F-Stop ICU Size Guide – Pick The Right One!

Share with your friends!

F-Stop pioneered the idea of removable camera inserts for outdoor photography backpacks. So much so that most photographers universally refer to these padded inserts using F-Stop’s product name – ICU (Internal Camera Units) – even when other brands offer similar products with different names.

The great thing about F-Stop ICUs and the F-Stop backpack system is that you can buy multiple to suit different days of photography. Some days you need to carry all your lenses and a couple of camera cameras. In contrast, other days, you need one camera, and a single camera tucked into a bag holding essential non-photographic gear. With the ICU system, you can configure your bag with one or more inserts and quickly switch them out as needed.

You’ve come to the right place if you need F-stop ICU details.

TIP: When the ICUs aren’t in your bag, many photographers, myself included, use them to organize their gear.

In this gear guide, I thought I would round up one of every size ICU currently available and document their size, specifications, possible payloads, and packing configurations in every F-Stop backpack. If you are about to buy an F-Stop pack and aren’t sure which ICUs to buy with it, you’ve come to the right place. Many people also use F-Stop ICUs in non-F-Stop bags, so these photos and specifications should also help with that decision. To show your appreciation for the time, money and effort I put into this guide, please consider using the links on this page to buy your F-Stop bags and ICUs. Thanks!

Table of Contents

There are two ways to approach this guide. You can use the detailed photos and specifications of each ICU to narrow down the options to the ones that will fit your gear. Or, you can click through to the section about a specific F-Stop backpack to find out which ICUs or combinations of ICUs fit into that bag. Most people should probably use both sections to get a clear idea of what they should buy.

ICU Specifications

Which ICU for Which Bag?

Discontinued ICU Models

Alternatives

Using Multiple ICUs In Combination

It’s common for photographers to buy multiple ICUs. For example, you might buy one that is the largest available ICU for your bag and a second smaller ICU that accommodates your “fast and light” setup – whatever that may be. This is the most common dual-ICU setup.

Another thing to consider is the simultaneous use of multiple ICUs. Two Small Pro ICUs are, for example, are the same size as a Large Pro ICU. These two ICUs can be stacked with openings facing the bag’s back panel, or “hatch-backed” (F-Stop’s term), where one of the two ICUs faces upwards with contents reachable from the bag’s top opening. You can choose to use both ICUs when you need to carry a lot of camera gear or just one when you need to prioritize pack space for outdoor gear.

The disadvantage with dual ICUs is you lack the single long volume capable of storing longer telephoto lenses. The advantage is that it is a slightly cheaper approach to owning two ICUs in some cases. In our example, two Small Pro ICUs are more affordable than buying a Large Pro and a Small Pro.

Some of the diagrams available from F-Stop show options for multiple ICUs, but be aware that they do not show all possible options. Frankly, there would be too many. Consider the internal dimensions of the bag you have, or the one you are about to purchase, and compare to the combined dimensions of the various available ICUs.


F-Stop ICU Specifications and Photos

Every currently available F-Stop ICU.

In this section, I have photographed every currently available F-Stop ICU and created side-by-side images of common combinations and size choices. Hopefully, this helps you choose perfect combinations or choose between two sizes when you are on the fence. While it’s impossible to photograph every type of camera and lens in each ICU, I have photographed the same camera and lens combinations next to and within each ICU. This should give you a clear sense of each ICU’s size.

Fit Notes

In the specifications, I have noted the bags into which each size of ICU will fit. Below this, I have added a “Best Fit” note. This Best Fit note indicates the most popular combinations of backpack and ICU. For example, the Small Shallow ICU technically fits into the largest Shinn backpack, but it would be swimming in there with no easy way to secure it. Thus, it is not a common combination.

Conversely, the XL ICU technically does fit into the Ajna Duradiamond, but the fit is very tight, and the zippers are hard to close. I wouldn’t go so far as to say they are incompatible because you might have a reason to use that combination, but it would not be my first recommendation for a bag+ICU combination.

Differing Interior Colours?

Eagle-eyed readers might spot that the interior colour of the ICUs appears to have some variation. Examining the labels, it turns out that some ICUs have been made in China, some have been made in Thailand, and some have been made in Vietnam. While the exterior fabric is identical to all three factories, the interior fabric colours vary slightly. This collection of ICUs has been acquired over many years, so the manufacturing location has likely been moved over time. I cannot say with any certainty which is the current manufacturing location or colour, nor does it matter. Aside from the interior colour shift, these are all identical, so this is a minor point.

Micro Tiny ICU

  • External Dimensions (in): 4 Depth x 6 Width x 8 Height
  • External Dimensions (cm): 10.2 Depth x 15.2 Width x 20.3 Height
  • Internal Dimensions (in): 3.25 Depth x 5 Width x 7 Height
  • Internal Dimensions (cm): 8.3 Depth x 12.7 Width x 17.8 Height
  • Weight: .18 kgs (0.4lbs)
  • Fits: Any F-Stop Mountain Series or Ultra-Light Series backpack

The Micro Tiny is the smallest in the ICU family. As demonstrated in the photos, it is precisely half the size of a Small Shallow ICU. This is an excellent size for a mirrorless camera with a single short zoom lens or a wide-aperture prime, plus a couple of spare batteries and an SD card holder. The Micro Tiny ICU is also a perfect size for a single flash with cables, batteries and radio triggers, or a GoPro kit with all the necessary mounts accessories. Although just half the width of any F-Stop pack, it still includes the hook and loop tab to secure it to the inside and prevent it rattling around when your bag isn’t full.

Micro Tiny ICU Price Check:


Small Shallow ICU

  • External Dimensions (in): 5 Depth x 11.5 Width x 8 Height
  • External Dimensions (cm): 12.7 Depth x 29.2 Width x 20.3 Height
  • Internal Dimensions (in): 4.5 Depth x 10.5 Width x 7 Height
  • Internal Dimensions (cm): 11.4 Depth x 26.7 Width x 17.8 Height
  • Weight: .32 kgs (0.71lbs)
  • Fits: Any F-Stop Mountain Series or Ultra-Light Series backpack

The Small Shallow ICU is twice the size of the Micro Tiny ICU. It’s the perfect size for a mirrorless camera with an attached short zoom or prime, with two extra lenses stashed alongside it. It’s also the ideal size for a body with an attached 70-200mm f/2.8 or 100-400mm zoom lens. The photos above also show the Small Shallow ICU alongside the Small Pro ICU, with the Small Pro being 2″ deeper and necessary for pro-sized or gripped bodies.

Small Shallow ICU Price Check:


Small Pro ICU

  • External Dimensions (in): 7 Depth x 11.5 Width x 8 Height
  • External Dimensions (cm): 17.8 Depth x 29.2 Width x 20.3 Height
  • Internal Dimensions (in): 6.5 Depth x 10.5 Width x 7 Height
  • Internal Dimensions (cm): 16.5 Depth x 26.7 Width x 17.8 Height
  • Weight: 0.42 kgs (0.93lbs)
  • Fits: Any F-Stop Mountain Series or Ultra-Light Series backpack
The Large Pro ICU is perfect for a 300mm f/2.8.

The Small Pro ICU is 2 inches deeper than the Small Shallow ICU to accommodate pro-sized camera bodies and gripped mirrorless or gripped DSLRs. If you do not have a pro or gripped body, the added depth of the Small Pro ICU allows you to carry a body with a lens attached, plus four additional short zooms or primes (see photo above). This ICU is also perfect for carrying drones alongside the remote control and several spare batteries.

Small Pro ICU Price Check:


Medium Shallow ICU

  • External Dimensions (in): 5 Depth x 11.5 Width x 11 Height
  • External Dimensions (cm): 12.7 Depth x 29.2 Width x 27.9 Height
  • Internal Dimensions (in): 4.5 Depth x 10.5 Width x 10 Height
  • Internal Dimensions (cm): 11.4 Depth x 26.7 Width x 25.4 Height
  • Weight: .43 kgs (0.95lbs)
  • Fits: Any F-Stop Mountain Series or Ultra-Light Series backpack
  • Best Fit: Guru, Kashmir, Loka, Lotus

The Medium Shallow ICU is perfect for a DSLR or mirrorless body with 4-5 lenses. The length of the ICU will accommodate a 70-200mm f/2.8 or a 100-400mm zoom attached, or not, to the camera body. Noteworthy is the photo in the gallery above that compares the side profile of the Medium Slope ICU to the Medium Pro ICU. As the name suggests, the Medium Slope ICU is deeper at one end to accommodate a pro-sized or gripped camera body.

Medium Shallow ICU Price Check:


Medium Slope ICU

  • External Dimensions (in): (Top: 5 Depth x 11.5 Width), (Bottom: 7 Depth x 11.5 Width) x 11 Height
  • External Dimensions (cm): (Top: 12.7 Depth x 29.2 Width), (Bottom: 17.8 Depth x 29.2 Width) x 27.9 Height
  • Internal Dimensions (in): (Top: 4.5 Depth x 10.5 Width), (Bottom: 6.5 Depth x 10.5 Width) x 10 Height
  • Internal Dimensions (cm): (Top: 11.4 Depth x 26.7 Width), (Bottom: 16.5 Depth x 26.7 Width) x 25.4 Height
  • Weight: .54 kgs (1.2lbs)
  • Fits: Any F-Stop Mountain Series or Ultra-Light Series backpack
  • Best Fit: Guru, Kashmir, Loka, Lotus, Ajna, Tilopa

The Medium Slope ICU should always be considered alongside the Medium Shallow ICU. Both are very similar, with the Slope version having 2 inches of extra depth at one end to accommodate a pro-sized or gripped camera body. This added depth can also help stow taller lenses, although it is not deep enough to vertically store a 70-200mm lens. Consider the 7-inch depth (at one end) carefully, and choose the Slope model if you have a camera body or lens taller than 5 inches but less than 7 inches.

A common question is whether the Sony 200-600mm lens will fit in the Medium Shallow or Medium Slope ICU. The answer is no. If you have a Sony 200-600mm lens, you will need to use either the Large Pro, XL Pro or Master Cine ICU. As demonstrated in photos shown in their respective sections.

Medium Slope ICU Price Check:


Large Pro ICU

  • External Dimensions (in): 7 Depth x 11.5 Width x 15 Height
  • External Dimensions (cm): 17.8 Depth x 29.2 Width x 38.1 Height
  • Internal Dimensions (in): 6.5 Depth x 10.5 Width x 14 Height
  • Internal Dimensions (cm): 16.5 Depth x 26.7 Width x 35.6 Height
  • Weight: .76 kgs (1.71lbs)
  • Fits: Kashmir, Loka, Lotus, Ajna, Tilopa, Sukha, Shinn
  • Best Fit: Loka, Lotus, Ajna, Tilopa

The Large Pro ICU can hold two camera bodies with 6-10 additional lenses depending on their size. With its Pro depth, this ICU can hold pro-sized camera bodies or gripped mirrorless or DSLRs. In the example photos, I have two cameras, a Sony 200-600mm, a Sony 70-200mm and three more prime lenses, with one slot remaining for my 1.4x teleconverter.

If you carry a Nikon Z 400mm f/2.8, it will not fit in the Large Pro ICU. That lens is 15″ long, and the internal length of this ICU is 14″. The Canon RF 400mm f/2.8 is 14.4″ long, so this is also too long, and that dimension doesn’t include the rear lens cap. On the other hand, the Sony 400mm f/2.8 is 13.5″ long, so this does fit, albeit snugly and without a camera attached.

Large ICU Price Check:


Extra Large Pro ICU

  • External Dimensions (in): 7 Depth x 11.5 Width x 19 Height
  • External Dimensions (cm): 17.8 Depth x 29.2 Width x 48.3 Height
  • Internal Dimensions (in): 6.5 Depth x 10.5 Width x 18 Height
  • Internal Dimensions (cm): 16.5 Depth x 26.7 Width x 45.7 Height
  • Weight: .93 kgs (2.06lbs)
  • Fits: Loka, Ajna, Tilopa, Sukha, Shinn
  • Best Fit: Tilopa, Sukha

The XL Pro ICU adds another 4″ to the length of the Large Pro, making it capable of holding all 200-400mm lenses, 400mm f/2.8 lenses, 600mm f/4 lenses and 800mm f/5.6 lenses. Although I don’t regularly shoot with those lenses, I still enjoy using the XL ICU with my Sony 600-200mm as it gives me a lot more room for additional lenses, filters and accessories.

XL ICU Price Check:


Master Cine ICU

  • External Dimensions (in): 8.25 Depth x 14 Width x 25.5 Height
  • External Dimensions (cm): 20.95 Depth x 35.56 Width x 64.77 Height
  • Weight: 2.24 kgs (5 lbs)
  • Fits: Shinn
  • Best fit: Shinn

Master Cine ICU Price Check:


Which ICU For Which F-Stop Bag?

Ultra-Light Series

Guru

F-Stop’s smallest Ultra-Light backpack, the Guru UL, can accommodate the Micro, Small and Medium-sized ICUs in any depth. The photos above give a clear view of the remaining space in the top of the bag when using any of the Small or Medium ICUs. The small size of the zippered back panel opening, and the curvature of the zipper, do slightly limit access to gear when the Medium Slope or Medium Shallow ICUs are used. This can be seen in the third photo, where some of the items in the bag are slightly hidden.

The Guru is a great all-purpose backpack that can quickly go from the city to the classroom and the mountains. Using a Small ICU with this bag is my preference, choosing a Small Shallow ICU with non-gripped bodies and a Small Pro ICU for pro-sized cameras and gripped bodies. If you only have a mirrorless body and one small lens, the Tiny Micro ICU is also great in this bag for everyday use when you always want to carry a camera with you.

F-Stop Guru Price Check:


Kashmir

Medium ICU in Kashmir

The Kashmir UL is 5L larger in volume than the Guru UL. It has a much larger back panel opening than the Guru (15.7″ vs 11″), this time allowing utterly unobstructed access to the gear inside a Medium Shallow or Medium Slope ICU for the perfect pairing. Of course, if you don’t need to carry that amount of equipment, you can safely use either of the Small ICUs.

The Kashmir UL is tall enough to hold a Large Pro ICU, but the zipper obscures access to the items at the top, and it leaves very little room above the ICU at the top of the bag. It is not my favourite combination. I think most people will be much happier bumping up in pack size to the Loka UL pack if they need the volume of the Large Pro ICU. The Loka’s extra 1.5″ of height and 1.3″ of added back panel opening height make for a much more usable combination.

F-Stop Kashmir Price Check:


Loka

The F-Stop Loka is similar in size to the Ajna pack from the Mountain Series. The recommended ICUs for the Loka are the Small, Medium and Large ICUs. The photos above give you a clear indication of how much additional space there is in the top of the bag with these three ICU sizes. Another great setup is hatch-backing a Medium Slope ICU with a Large Pro ICU, as seen in the photo below.

Loka with Large Pro ICU stacked on a Medium ICU.

The XL Pro ICU does fit in the Loka, but it’s tight, and I don’t recommend it. The 17″ back panel zipper obscures many of the XL ICUs contents. If you are set on having a smaller pack size but carrying the XL ICU, I would recommend using the F-Stop Ajna instead. The pack is similarly sized, but the zippered back opening is one inch taller, thus obscuring less of the ICU’s contents.

F-Stop Loka Price Check:


Mountain Series

Lotus

A Medium Slope ICU in the Lotus.

The 32L F-Stop Lotus is essentially a shorter version of the Ajna, designed as an option for people with a shorter torso. This shorter height also keeps the bag’s weight well centred on your back, making it an excellent choice for very active pursuits with a camera on your back, such as Mountain Biking.

The Large Pro ICU is the largest option for the Lotus, but it is a very snug fit and leaves no more room in the bag’s top section. The best ICU for the Lotus is either the Medium Slope or the Shallow Medium, with the Small Pro and Small Shallow also making great options.

F-Stop Lotus Price Check:


Ajna

The Ajna is F-Stop’s second-best seller after the Tilopa. Although the bag’s overall volume is around 10L less than the Tilopa, much of that difference comes down to the smaller front pocket on the Ajna. This means that the bag’s main compartment is nearly the same size as the Tilopa’s, and as a result, ICUs fit similarly in both of them. Comparing the dimensions provided by F-Stop, both Ajna and Tilopa have an internal height of 20″ and a zippered back panel opening that is 18″.

Dimensions only tell part of the story, though. These bags are not perfectly cubic, and the Ajna’s tighter taper makes the XL ICU a much tighter fit in this bag than it is in the Tilopa. As you can see from my photos, it does fit, but the zippered closure is tighter, and there is zero room left on the top of the bag. As a result, my preferred ICUs for the Ajna are the Medium Slope and the Large Pro.

The XL Pro ICU is useable, but I would only recommend this if you had a particular need to carry that much gear in a very tightly packed, efficient way. For example, let’s say you want to take a 600mm lens on several international flights with very tight carry-on restrictions. In this case, shoving the XL Pro ICU into the Ajna makes a lot of sense. The Ajna is a tighter package with thinner padding on the harness and fewer external “dangly bits”. This makes the bag look smaller than the Tilopa and fit far easier into overhead lockers while still carrying a similar camera payload.

F-Stop Ajna Price Check:


Tilopa

The 50L size of the F-Stop Tilopa is a real sweet spot in the lineup. It is little surprise that this is the most popular bag in the F-Stop lineup, and 15 years after its original launch, this bag has been tweaked to perfection with the newest Duradiamond version.

In my opinion, the two best ICU options for the Tilopa are the Large Pro ICU and the XL Pro ICU if you are carrying a lot of camera gear. Use the smaller ICUs if you have a lot of non-photographic equipment to carry. F-Stop primarily recommends the Large Pro, and this is the one available with the bag if you buy the “essential bundle” package. The 18″ back panel opening of the TIlopa gives you unobstructed access to the contents of a Large Pro ICU.

Those that want to carry 400mm, 600mm and 800mm super-telephoto lenses will need to use the XL Pro ICU. As you can see from my photos, the XL Pro ICU does extend slightly beyond the zippered back panel opening. If you are tucking the end of a large telephoto lens up into that section, this overlap has zero effect on efficiency and usability.

Both options, Large Pro and XL Pro, still offer some room on top of the ICU inside the bag’s top zipper. Plenty of room for small compressible items such as gloves or hats. Of course, the Large Pro ICU is 4″ shorter than the XL version, so this gives you 4″ of extra space in the top section.

F-Stop Tilopa Price Check:


Sukha

Large Pro ICU with hatch-backed Small Pro ICU in Sukha. Photo: F-Stop Gear.

When the Sukha was initially launched, it came with the Master Tele ICU. This has been discontinued, and the XL Pro ICU is now the recommended pairing. Another great combination is the Large Pro ICU, with a hatch-backed Small Shallow ICU on top for storing a drone or simply as a protected place to keep your lunch.

The Sukha is an excellent backpack for wildlife photographers that want to carry large super-telephoto lenses such as a 600mm or 800mm lens in the XL Pro ICU. I do think it’s a shame that F-Stop discontinued the Master Tele ICU, though. For filmmakers, the added size of the Shinn pack and the Master Cine ICU is a better fit for rigged cine cameras such as REDs, Canon C300/C500 and Sony FX6/FX9.

F-Stop Sukha Price Check:


Shinn

Most F-Stop backpacks have an internal width of 11.5″; thus, all Small, Medium, Large and XL ICUs are 11.5″ wide. However, the F-Stop Shinn backpack is 14″ wide, and for this reason, it needed a dedicated ICU called the Master Cine (or Cine Master, depending on which part of the F-Stop website you read).

My recommendation is to use the Master Cine ICU with this bag. Using any of the 11.5″ wide ICUs leaves gaps around the ICU where your other gear gets trapped. If you are going for the colossal capacity of the 80L Shinn pack, you should probably go the whole hog and pair it with the Master Cine ICU. As the name suggests, this is a combination that is perfect for large Cine rigs such as REDs, Sony Cine Alta, and Canon Cinema EOS cameras.

The exception will be explicitly using the Shinn for overnight camping with camera gear. The size of the Shinn makes it one of the few camera bags on the market capable of carrying a tent, sleeping bag and other overnight essentials, alongside a still-substantial amount of camera gear. In this case, choose whichever smaller ICU you need, and pay attention to how you pack gear around it to make sure it is well secured.

F-Stop Shinn Price Check:


Discontinued ICU Models

As far as I know, the ICUs listed below have been discontinued. When writing this guide, I was able to source some of them on third-party websites through Google searches, but it’s anyone’s guess how long that stock will last.

Mico Nano ICU

  • External Dimensions (in): 4 Depth x 6 Width x 4 Height
  • External Dimensions (cm): 10.2 Depth x 15.2 Width x 10.2 Height
  • Fits: Any F-Stop camera bag

Designed for GoPros and point and shoot cameras, the Micro Nano ICU is the smallest model in the ICU lineup. It could easily be argued that these days, the padded F-Stop accessory pouches are a much better solution for protecting that kind of gear.


Master Tele ICU

  • External Dimensions (cm): 20.95 Depth x 29.21 Width x 66.04 Height
  • External Dimensions (in): 8.25 Depth x 11.5 Width x 26 Height
  • Weight: 2.33kg (5lbs)
  • Fits: Sukha and Shinn
  • Recommended Use: Sukha

Originally developed and launched alongside the first version of the Sukha backpack, the Master Tele ICU can hold up to an 800mm lens with a pro-sized camera body attached. The Master Tele ICU has a zippered front opening and a zippered top panel, which allows you to pull a super-telephoto lens vertically out of the top of the backpack. With the discontinuation of this ICU model, the only ICU with a zippered top panel for vertical extraction is the Master Cine ICU which will not fit in the Sukha. The recommended ICU for the Sukha is now the XL Pro ICU.


Medium Pro ICU

The Medium Pro ICU has been discontinued in name only. It has simply become the Medium Slope ICU. I had to think about this one and find some old photos taken over a decade ago to jog my memory. You can see the slope in the design of what was, back then, called the Medium Pro ICU.


Large Slope ICU

A very old archive photo of the now discontinued Large Slope ICU.
  • External Dimensions: Top: 127 x 292 x 381mm Bottom: 165 x 292 x 381mm
  • Internal Dimensions: Top: 114 x 267 x 356mm Bottom: 165 x 267 x 356mm
  • Weight: 0.73KG

An old blog post I wrote tells me that the Large Slope ICU was introduced way back in March 2013. I’m not sure when this model was discontinued, but I don’t think it lasted long in the lineup, with most people preferring to use the Large Pro ICU.


Shimoda Core Units as an Alternative

Shimoda Core Units

Shimoda Designs make a similar selection of padded camera inserts for their adventure photography backpacks. The size of their Core Unit camera cubes closely mirrors the F-Stop ICU sizing, and I have known people to mix and match between these brands. If you’d like to find out more about these options, look at my guide to Shimoda Core units.

Photo of author

Dan Carr

Professional photographer based in Yukon, Canada, and founder of Shutter Muse. His editorial work has been featured in publications all over the world, and his commercial clients include brands such as Nike, Apple, Adobe and Red Bull.

You may like

Leave a Comment

Your email address will not be published or shared. Please note that if you include a link in your comment, it will have to be moderated first before it appears on the site. Required fields are marked*

By submitting a comment this form also collects your name, email and IP address so that we can prevent spam. For more info check our privacy policy.