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Atom Packs “The Mo” 50 Backpack Review

Atom Packs The Mo 50 Backpack Review

The Atom Packs “The Mo” 50L is a beautifully crafted internal frame backpack made across the pond in England. Weighing 32.1 oz (910g) and made with waterproof Ecopak EPX200, it’s a roll-top backpack that’s loaded with features and pockets that will appeal to most thru-hikers and hill walkers. I’ve been particularly impressed with that pack’s frame and suspension system, which is capable of carrying surprisingly heavy loads with great comfort and ease. If you’re looking for a highly functional backpack that has a unique edge to it, check out Atom Pack’s, “The Mo.” They also provide no-hassle shipping to the USA.

RELATED: 10 Best Ultralight Backpacks

Specs at a Glance

  • Model: Stock Pre-Built; also available as a custom pack
  • Volume: 45L in main body + 2.5L in each side pockets + 5L in front mesh pocket (not counted in total)
  • Weight: 32.1 oz (910g)  (torso medium, hipbelt medium)
  • Weight Tested:  33.6 oz(953g) (torso medium, hipbelt xl)
  • Gender: Unisex
  • Torso Lengths Available: 15-17″, 17-19″, 19″-21″, 21-23″
  • Pockets: 6
  • Shoulder Straps: S-shaped
  • Frame: Plastic framesheet and center aluminum stay
  • Load Lifters: Yes
  • Hydration Compatible: Yes
  • Material: Body-Ecopak EPX200; Side pockets -Robic Extrema; Mesh – Dyneema Mesh
  • Seam-taped: No
  • Bear Canister Compatibility: BV500 and BV450 fit vertically
  • Mfg Recommended Base Weight: 22 lbs (10kg)
  • Mfg Max Recommended Load: 42 lbs (19kg)

Backpack Storage and Organization

The Mo has a standard roll top design with side water bottle pockets and a front mesh pocket.
The Mo has a standard roll-top design with side water bottle pockets and a front mesh pocket.

The Mo 50 is a standard, but stylish roll-top pack, that looks really cool in black Ecopak with orange highlights. I never thought I’d like a black backpack before, but this pack is stunning. The interior is white, however, so you can actually see what’s inside.

While the pack fabric is waterproof, the seams are not sealed, so I’d still recommend lining the inside with a plastic bag. The main compartment is hydration compatible with a hose port over each shoulder strap. There is an internal strap and hook inside to hang a reservoir, but no internal pocket to hold it in place.

The side pockets have an elastic cord tensioner w:cordlock to keep bottles from falling out.
The side pockets have an elastic cord tensioner w/cordlock to keep bottles from falling out.

The Mo has two side water bottle pockets that can fit two SmartWater bottles or two 1L Nalgene bottles side by side. The bottles are reachable when wearing the pack. The side pockets have an elastic cord/cordlock combo to secure the bottles along the top and drain holes in the bottom to remove moisture. The pockets are made with “Robic Extrema”, which is just Robic nylon with High-Density Polyethylene Fibers (HDPE) fibers running through it and is easy to patch with Tenacious Tape if you hole it.

The ends of the roll-top can be buckled to the sides of the pack with long webbing straps or together on top of the main compartment. If buckled on top, you can loop the side webbing straps around the front of the pack for added compression or to attach gear like snowshoes or a foam pad. The top of the roll-top has two plastic snaps to hold the top closed before rolling.

The top of the rolltop is held closed by snaps.
The top of the rolltop is held closed by snaps.

The Mo also has a bottom stretch pocket on the base of the pack, which has really just become a popular feature on backpacks in the past two years. Many people use it to stash a day’s worth of snacks and food, or hats and gloves, so they can be reached while you’re walking withing having to stop. One end of the pocket is completely open, while the other has a small trash hole where you can stuff candy and snack wrappers for disposal later.

I really like this bottom stretch pocket because I don’t like to take food breaks when I hike, but I’m also not very good at snacking to keep my energy up and rely on willpower instead. But I can stash quite a bit of food into this bottom pocket and pull it without stopping, which I’ve really come to appreciate the more I use the pack. Old dogs can learn new tricks.

The bottom stretch pocket is open on one side so you can reach in and pull out items without stopping.
The bottom stretch pocket is open on one side so you can reach in and pull out items without stopping.

The bottom stretch pocket is made with the same Dyneema mesh found on the front pocket, but I can’t say how long it will last if you put your pack on the ground. That’s usually the highest abrasion point on a backpack and all fabrics break down there eventually. While Dyneema fibers are strong, the Dyneema mesh is primarily nylon 6.6 which isn’t particularly abrasion resistant for this application. Ask me about it in a year or two, because I’ll probably still be using this pack then.

The front pocket is made with Dyneema Stretch Mesh.
The front pocket is made with Dyneema Stretch Mesh which is Nylon 6.6 reinforced with Dyneema fibers.

The front stretch pocket can hold 5L of items but is not included in the 50L volume of the rest of the backpack. It has enough stretch though that you can get a 1L cookpot into the pocket when the pack is packed tight. There are also seven fabric loops sewn into the seams of the front pocket which Atom has threaded with elastic cord. I’ve left it in place for illustration, but I usually remove cords like them as soon as I get a pack that has them. I hike off-trail a lot and you don’t want elastic cords hanging off a pack for that kind of thing.

Backpack Frame and Suspension

The thing that makes The Mo backpack “sing” is the frame, the hip belt, and the fact that the pack is slightly narrow (10.5″ wide by my measure) like a climbing backpack. All that makes it super comfortable to carry, with a hipbelt that doesn’t slip and a frame capable of a maximum carry of 42 lbs (says Atom Packs). I think that’s pretty close although you’ll have a hard time fitting that much heavy gear or water into or onto the pack. I’ve carried up to 33 lbs with it on long water carries and felt that I could have carried even more weight if necessary.

The internal frame is a plastic sheet with a single aluminum stay.
The internal frame is a plastic sheet with a single aluminum stay.

The Mo frame is a shaped plastic sheet with a center aluminum stay which comes pre-bent but can be bent and modified if you need something a little different. Both terminate in the center of the pack, behind a modest lumbar pad on the hip belt. Both frame components are removable, but there’s little reason to. In addition, the back of the pack behind the shoulder straps is padded with 8mm closed cell foam and covered with 500D textured nylon, which has a softshell look and feels good against your back.

The hipbelt has a modest lumbar pad.
The hipbelt has a modest lumbar pad.

The hip belt has a single center buckle with two tiers of webbing straps so you can tighten it to match the shape of your hips, enabling a customized fit for both men and women. The hip belt is 4″ wide, backed with spacer mesh, and lightly padded, with a modest lumbar pad in the back which helps keep the pack in place on the hip girdle. The hip belt is replaceable if you need a different size and is held in place by velcro behind the lumbar pad.

The hip belt has a two-tier adjustment system and does not slip. Great hip belt.
The hip belt has a two-tier adjustment system and does not slip. Great hip belt.

The Mo does not come with hip belt pockets, but Atom Packs sells them as an optional add-on. They slip over the hip belt and are held in place by front and back webbing loops. The pocket that came with my pack is made with waterproof Ecopak and has a waterproof zipper, but the ones listed for sale on the website are only made with Robic Extrema. I’d inquire if you want one with waterproof fabric.

Hip belt pockets are available but sold separately
Hip belt pockets are available but sold separately.

The shoulder straps are S-shaped, so they’ll work for men and women, curving around the sensitive bits They’re also lightly padded and backed with spacer mesh. Both straps have daisy chains sewn on the front, but they’re both covered with sewn-on and non-removable stretch mesh pockets sized for a Smartphone or snack bars. Despite this, you can still access the daisy chains under them and move the sternum strap up or down.

I wasn’t initially thrilled with these pockets, because I like adding my own accessory pockets that I move between my backpacks. But I got used to the ones on The Mo pretty quickly and found I liked them. The elastic mesh they’re made with holds onto your phone even if you bend over, but doesn’t provide any moisture protection in rain. The pockets are an option on the custom 50L Mo, so you can opt to not have them added to the pack if you’re willing to wait for a custom pack to be made.

Both of the shoulder straps have sewn on stretch mesh pockets.
Both of the shoulder straps have sewn-on stretch mesh pockets.

External Attachment Points and Compression

I’ve touched on a number of the external attachment points already including the webbing loops and elastic cord surrounding the front stretch pocket, the shoulder strap daisy chains, and hip belt attachment loops. The Mo also has a top Y strap which is good for securing a foam pad or bear canister to the top of the main compartment. There’s also an ice axe loop and a bungee cord to secure the shaft.

Orange elastic cord is threaded through loop on the side of the pack to attach extra gear.
Orange elastic cord is threaded through loops on the side of the pack to attach extra gear.

In addition to the top compression provided by the roll top’s side straps, The Mo comes with elastic cords and cord locks along the sides of the pack. But they really don’t provide any compression capability, even if they’re replaced by static cord. The cord is simply not thick enough to compress the pack. Their real function is to secure objects, like trekking poles or a Tenkara rod to the side of the pack so they don’t fall off.

You can remove the elastic cord, of course, and slide webbing straps with gatekeeper clips through the webbing loops that anchor the cords if you want more effective compression plus an attachment point. But honestly, I’ve never understood why ultralight and lightweight pack manufacturers opt to use side cords instead of webbing, when doing so removes any compression benefit.

The Mo comes with a top Y strap and load lifters.
The Mo comes with a top Y strap and load lifters.

Comparable Ultralight Backpacks

Make / ModelWeightFabric
Zpacks Arc Haul 60L20.9 oz / 593gUltra 200
Hyperlite Mountain Gear Southwest 5534.9 oz / 989gDyneema DCF
Granite Gear Crown 3 60L32.6 oz / 1040gRobic Nylon
Osprey Exos Pro 5534.6 oz / 981gUHMWPE Nylon Ripstop
ULA Circuit 68L37.3 oz / 1038gRobic Nylon
Gossamer Gear Mariposa 60L34.2 oz / 968gRobic Nylon
REI Flash 55L45 oz / 1276gRobic Nylon
Gregory Focal 5841.3 oz / 1171gRobic Nylon
SWD UL Long Haul 5030.2 oz / 856gUltra 200
Durston Kakwa 5531 oz / 880gUltra 200


Atom Pack’s “The Mo” is available as a stock model with a set of standard features or as a custom build with your choice of colors and other options. I think the stock all-black model, reviewed here, is stunning, not just in its appearance but also functionally. The pack carries wonderfully due in large part to its unique frame and narrow dimensions, its highly adjustable hip belt and easily accessible pockets which are reachable while you’re in motion. I really can’t think of any backpack that I currently own and would rather carry than The Mo 50. It is an exceptional lightweight backpack that can hold its own with moderate loads and put a smile on your face. Highly recommended!

Disclosure: Atom packs donated a backpack for review.

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  1. The best pack on the planet by far – I used the Mo this year on my PCT hike – we only made it the first 750 miles but it was super comfortable, held everything I needed and I have no doubts that it would have lasted the entire hike to Canada.

  2. Bill in Roswell GA

    Philip, as the Mo is only 10.5 in. wide, can it hold a bear canister, like a BV 500? Or would a bear can have to ride under the Y strap? Sounds like an awesome UL pack!

  3. Excellent Review! I was just reading about this BP over the weekend, so nice to see your detailed review today. I recently read your review of the ULA Ultra OHM which was also quite glowing. How do these face off? At 57, I’m sold on going more or less UL and embrace the simplicity. I do wonder about the lack of ventilation and back sweating – have you had to deal with that? Lastly, I’m a little concerned with Atlas being a UK company and not being able to test out the pack before I buy (or the return policy being complicated and expensive…)

    • We live in an age with lots of great choices. The ohm is a really sweet pack too. But neither address the back sweating issue. The ohm has the advantage of being a bit adjustable in the torso length because the hip belt can move up 2″. And of course, it’s also available in Ultra which is more durable than Ecopack EPX200 (both are waterproof). Think about the pockets (shoulder/hip) on both packs and what you prefer in terms of cost and wait times. You really can’t go wrong either way.

      • You aren’t kidding on the UL options right now. I also have The Hyperlite – 3400 Junction high on my list. Being from Seacoast NH and having a connection with the Biddeford area, I like that they are local on top of being rated as excellent packs. Thanks!

        • They were local. After opening their factory in Biddeford and taking lots of venture capital investment from the state of Maine, they moved all of their production to Mexico last year. Of Hyperlite and ULA – ULA is the only one to still make their packs in the USA. Zpacks also makes them local to the US.

        • Seek Outside, SWD, Zimmerbuilt and more are MUSA (Made in USA), plus the others already mentioned. Atom’s look really sweet so I’m trying not to swoon too hard compared to some of our local makers.

      • Scott Douglas Fortune

        Shame such a great company and product pack it up and go to Mexico for production.

        May not be that big of deal but stuff like this can be the final thought to buy it or leave it.

        A small amount of our gear (and i get it) does come from abroad.

        Happy Trails.


    • Take a look at the SWD Long Haul series as well. I was actually torn between the Atom and the Long Haul 35 and chose the SWD since it was my original choice when I bought my Ohm. At the time I needed a pack quick and couldn’t wait for a custom order. In the end the Ohm and I didn’t get along and I hated how the mesh pocket tapered at the bottom of the pack. It reminded me of the rear end of a VW Bug! Anyway, the SWD has been fantastic and I’ve got no complaints whatsoever with it. Even when I need to carry a BV450 there’s enough room for a 5 day trip. It’s definitely more enjoyable with a food bag though.

      That all said, I plan on ordering a custom EP30 Atom pack for hut hiking in Europe. You don’t need much room for gear when you’re sleeping in huts and with the exchange rate being what it is currently it makes sense. The current wait time isn’t too bad and I’m in no huge hurry at the moment.

  4. I am torn between the Mo 60, Waymark Embr and ULA Circuit. What are the main differences between the 3 packs? Would also prefer a pack with a bit more cushy shoulder straps and hip belt.

    • If you don’t mind me asking, why those three, and why can’t you decide between them? It will help narrow the scope of my answer and give me a better idea of what’s important to you.

      • I tried all of the women specific backpacks at REI, the Zpacks Arc, OV Shadow Light and own a Gossamer Gear Mariposa. Mariposa didn’t ended up being the right one after all. Basically I tried a bunch and still haven’t found the right fit. Atom the MO and ULA Circuit seem to be liked very well. Waymark just seems to fit right in with ULA and the MO.

        • If you’re looking for a woman’s pack (sizing), you’ve been looking in the wrong place. Go to ULA – they’ve been catering to female hikers since day one and have the best size range and features designed for female hikers. Personally, I’d rather use the Ohm than the Circuit. try both. The thing that sets ULA packs apart from others is 1) their hip belt – probably the best in the business, and 2) you can move the hip belt up or down where it attaches to pack in order to dial in an exact torso length, 3) J-shaped shoulder straps.

  5. I have a custom version of the Mo and it is by far the best pack I’ve ever owned. A superbly comfortable carry. Paying extra for the custom version allowed me to choose the colour for each panel, and of the bungee cord and so mine is, in my opinion, a thing of beauty :-)

    More importantly, I had mine custom made for my back length (I’m pretty tall!). Being lucky enough to live in England near to where Atom Packs are made meant I could go along and my back and hips were measured by Tom, Atom Packs’ owner, so the fit is superb. But if buying from the States, and thus you can’t avail yourself of that, I’m confident you’ll still be impressed with the pack – its comfort, features and build quality.

    I have, by the way, no affiliation with Atom Packs. I’m just a very happy customer.

  6. Did anyone have a problem with NO sleeve for the hydration bladder?

  7. how does this pack stack up against the Dan Durston Kakwa 40? they seem similarly optioned, weights are close, and carry weights are similar. curious to get your take given this pack wasn’t in your list in the article.

    • One of my trusted reviewers, Greg, wrote a very detailed review of the Kakwa. I had him do the review instead of me because the hip belt turned out to be way too short for me to use and didn’t match the original spec. Greg is smaller than me, so I gave it to him. Here’s a link to his review.

      I can’t give you a hands on comparison since I couldn’t use the pack. But the biggest difference between these two packs is volume. A 40 liter pack isn’t comparable to a 55 liter one. Dan is working on a 60 liter model and says he will make the hip belts longer this time. But I have no idea when it will be available.

  8. I think you’re confused. Hyperlite Mountain Gear moved their manufacturing to Mexico, but Atom Packs is made in the UK and I’m pretty sure Durston Gear manufactures their stuff in Vietnam.

  9. Can you provide your height in reference to the medium torso size of the pack tested? Thank you.

    • I’m 5’11”, but you should be basing your pack sizing choice on your torso size and not your height. The two are independent of one another. If you don’t know how to measure torso length, google it.

      • Curious. What is your torso length? I am also 5’11” and have a torso of a bit below 20” ( 50-50.5cm) and am on the fence between Medium and Large (sometimes I feel that I get smaller backpacks to sit better around waist/hip)

        • I’ve come to that realization myself. Finally, I think I have figured out why packs slide down on me; no real hips to speak of. My torso measures 19.5″, but an adjustable pack set at 18″ works much better for me. I bought a Mo based on the 19.5″ measurement but it’s a no-go, even with the lumbar pad. Waiting for their restock to get a shorter torso model. RE: height and torso length, I’m 6’2″ with that 19.5″ torso, while one of my backpacking buddies is 5’8″ with a 21.5″ torso! He says if his legs weren’t so short, he’d be tall!

        • I have an 18.5″ torso, but I think I got a 19″ with this pack. Worked perfectly. You just have tp keep trying until you find “the one”.

  10. Hey Phillip,
    Really appreciate all your reviews and opinions. I’m stuck between the Gorilla 50 and an Atom+/Mo. I’ve previously owned a Mariposa 60 and found it comfortable, but ultimately didn’t love the big side pocket and lack of compression when carrying small loads. I also tried an SWD Movement 35 but the floating hip belt was not for me.
    My main concerns with the Gorilla is the lid closure, same as Mariposa which I didn’t love, and the thinner materials/durability concerns.
    My main concern with the Atom+ is lack of carrying comfort and no side-compression attachments for the roll-top.
    My main concern with the Mo is the cost (lack of pre-built Mo 40 option and shipping).
    Enough of my ranting, I see that you have pretty rave reviews for both Gorilla 50 and Mo, if you had to choose one which would it be? And any thoughts on the Atom+?
    Thanks abunch!

    • Kind of difficult for me to advise you since I don’t know what you want to use the pack for. But if you hate the lid on the Mariposa, you’ll still hate it on the Gorilla.

      • Hah, that’s what I figure for the Gorilla lid.
        I do mostly 3-5 day section hikes in the Sierras so I need to carry a bear can most of the time. Baseweight varies between 11-14 lbs with bear can. Also some shorter alpine climbing 2-3 day trips where I need to bring climbing gear. Mariposa was plenty large for all my gear.
        Is there a compelling factor that would make you choose the Gorilla over the Mo, or vice versa?

        • I think the Gorilla framestay will do a better job of keeping sharp-edged objects off your back and that it’s easier to strap stuff to the side of the Gorilla. But if durability is more important, I’d go with the Mo. Come to think of it, if you’re carrying climbing gear the Mo will be better. The nylon on the Gorrilla and Gossamer Gear packs, in general, is really thin.

  11. I love the review and all these.comments. I was looking at ultralight and am amazed at all the options. I’m in Canada and we have the Howling Huron and Mec has some new ones that are similar to the Atom. I am looking for a women specific small torso that has the ability to be frameless and that I can easily use for scrambling while backpacking in the Whites. I had a Gregory and it kept coming over my head while I was trying to scramble going up the Wildcats and I basically could not see where to reach…so the Atom being narrower might be an option. Open to suggestions. I’d also use to carry my snowshoes in the winter hiking season.

  12. What do you think carries an initial load of 30 lbs better, the Mo or the SWD Long Haul 50? They both look like they have comfortable hip belts and shoulder straps, but in terms of load transfer? The SO Gila is 6-8 oz heavier but maybe an overkill for that load?

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