Outdoor Vitals CS40 Backpack Review

Outdoor Vitals CS40 Ultra Backpack Review

The Outdoor Vitals CS40 Ultra Backpack (shop now) is a new and lighter-than-average contender in an elite group of best-in-class, internal frame ultralight backpacks made with Challenge UltraWeave fabric. We immediately consider it to be a top performer and recommend it highly.

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  • Weight: 27 oz
  • Price: $368
  • Materials: Challenge UltraWeave 200
  • Frame: 2 Carbon Fiber Stays, Foam Back Panel
  • Load Capacity: 35 lbs
  • Internal Volume: 41L
  • External Volume : 12L
  • Pros: Very ultralight. Challenge ULTRA fabric is durable and waterproof. Comfy. Load lifters. Premium performance.
  • Cons: Expensive. Rear pocket is stretch mesh. Side pockets are a bit small. 40L size is less versatile than 50L+.


Outdoor Vitals CS40 Ultra front side

Materials and Frame

Anyone writing an Outdoor Vitals CS40 Ultra Backpack review must start and end with the use of Challenge UltraWeave, aka ULTRA. Still relatively new to market, this best-in-class wonder fabric beats Dyneema at its own game, as it is lighter weight and more durable, while still offering full waterproof protection. CS40 Ultra uses white, rather the typical gray, which stands out and looks flashy, though we assume it will eventually turn to an off-white beige as it gets old and dirty.

close up on the UltraWeave Fabric

When it comes to materials, we also love the two ounce carbon fiber stay frame, which lends structure, transfers weight to hips, and allows for functional load lifters. In conjunction with the aerated foam back panel, hiking with the Outdoor Vitals CS40 Ultra Backpack pack proved to be very comfortable, especially compared to frameless packs in a similar weight class. The entire package makes for an excellent carry.

cs40 ultra load lifters

The foam used in the hip belt (which has a lovely reverse-pull) and back panel has lots of cut outs to reduce weight and add ventilation and its generally quite comfortable. The shoulder straps are complimented with spacer mesh for volume and additional breathability. The sternum strap is very easy to adjust.


Pockets Review

Perhaps the only materials choice we disagree with is the use of stretch mesh for the rear pocket. While it is more pleasant, more transparent, and overall easier to use than static materials or opaque stretch weave fabrics, stretch mesh has a poor track record of being prone to snags, tears, and rips. It also fails to protect the contents from abrasion. If, for example, you carry your rain gear in the rear mesh pocket, set the pack down on some rocks at a break, and then used the pack as a backrest while you sit and snack, you might find your rain gear gets a bit scraped up.

outdoor vitals cs40 ultra backpack review of mesh rear pocket

While this iteration of stretch mesh performed marvelously on our first trip out and sustained no damage whatsoever, we question its long term durability and are surprised they didn’t use UltraStretch.

There’s things to like and dislike about the side pockets. For starters, they are made with the same durable UltraWeave 200, are shaped like cup holders with flat bottoms, and SmartWater bottles sit nicely in them.

close up on side pocket

On the flip side they are a bit smaller than average compared to similar ultralight packs, and are definitely on the shallow side. They’re not very good at storing non-water bottle types of items. It seems like they’ve designed these pockets to make it so you can reach back to grab bottle while wearing the pack, and if that something you’d use, then that’s a plus side.

However, this reviewer has never had that kind of shoulder mobility and found the shallowness to be disadvantageous.  Because they have no cinching mechanism, because UltraWeave is a slippery material, and because the CS40 doesn’t stand upright on the ground without leaning against something, we found that at breaks, water bottles were prone to falling out of the side pockets when setting the pack down if it ever tipped over. Nothing ever fell out while moving, so not a huge issue. But worth noting.

shoulder strap pocket

Lastly, we also nod to the hip belt and shoulder strap pockets. The hip belts pockets are structured, and adequately sized for storing multiple snacks each, though we would have preferred them to be a bit larger still. The OV Shoulder Strap Pocket, which we love and highly recommend, was great for storing a Katadyn .6L filter and could also fit up to a 700ml Smartwater.

hip belt pockets


Features Review

The use of static side-compression-cords with line locks (as opposed to shock cord) was interesting, but proved functional at holding a sit pad or hanging socks to dry. It has a dedicated ice axe fold over loop at the bottom and cinch-able cord at the top for easy carry.

side compression straps

CS40 is a roll top closure with mid sized buckles. There are no side buckles, so  you can only close off the main compartment at the top center. A single compression straps runs over the top, we wish it were a Y-compression strap, but it is simply a single line.

Outdoor Vitals CS40 Ultra backpack roll top closure


Size and Shape Review

We found the Outdoor Vitals CS40 Ultra Backpack to be on the taller and more narrow side, offering excellent elbow and/or reach back mobility. The height is required for functional load lifters. That said, it might interfere with 360 brim cap. The author doesn’t mind shorter wider packs for this reason, but found this shape to be perfectly functional and pleasant to wear.

side view of outdoor vitals cs40 ultra backpack review

Note that the 40L namesake size undersells the total volume slightly. When you add in external storage, it’s actually a 53L. The 41L main compartment volume is perfect for storing an ultralight load.

But we wish it were also available in a 50-60L main compartment volume option, which we consider to be the most versatile and universal size. 55L are compatible with shoulder season gear, week-long food carries, and non-ultralight gear, and often weigh only 1-2 ounces more than their 40L counterparts as additional fabric is the only add-on.

Outdoor Vitals CS40 Ultra Backpack Review Verdict

If you want a top tier, fully-featured, lighter-than-average ultralight pack, the Outdoor Vitals CS40 Ultra Backpack is well-worth considering. It’s durable and waterproof thanks to UltraWeave, and has great comfort and load transfer thanks to the carbon fiber frame. Despite a few minor quibbles with their pockets, we give this pack a very strong seal of approval.