Durston Kakwa 55 vs Outdoor Vitals CS40 Ultra Backpack

Editorial Team
Last modified at July 22, 2026
When it comes to ultralight backpacks, the Durston Kakwa 55 and the Outdoor Vitals CS40 Ultra are two top contenders. Both packs offer exceptional durability and comfort, but they cater to slightly different needs and preferences. The Kakwa 55 is renowned for its comfort on long-distance hikes, while the CS40 Ultra stands out for its balanced performance in various weather conditions.

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Durston Kakwa 55Outdoor Vitals CS40 Ultra Backpack
Kakwa 55
CS40 Ultra Backpack
Weight

Ultra 200X: 30.1 oz (S), 31.5 oz (M), 32.4 oz (L); UltraGrid: 29.2 oz (S), 30.6 oz (M), 31.3 oz (L)

27 oz (size M torso with M hip belt)

Capacity

55 L

51 L total (S); 53 L total (M/L)

Fabric Type

Ultra 200X or UltraGrid

Challenge UltraWeave 200 UHMWPE/polyester blend

Hip Belt

Dual strap design with reverse pull 2:1 leverage for easy tightening; redesigned for 2026 with lumbar pad and improved durability

Full size fully padded load-bearing hip belt

Seam Sealing

No — not factory seam-taped; optional user seam sealing

No — sewn seams are not seam-taped

Warranty

Lifetime

Performance Promise (see Warranty Info)

Fabric Denier

Ultra 200X: 200D; UltraGrid: 210D nylon with 200D UHMWPE grid

200D

Hip Belt Size

S/M: 29–38 in; M/L: 33–42 in

XS: 25.5 in; S: 27.25 in; M: 30 in; L: 34 in; XL: 36.25 in (padded belt lengths)

Side Compression Straps

Yes

Yes — three-point side-compression cords

Roll Top Closure

Yes

Yes

Durability

Kakwa 55

4.4/ 5.0

CS40 Ultra Backpack

4.4/ 5.0

Durability is crucial for ultralight backpacks as it ensures the pack can withstand the rigors of long-distance hiking and rough terrain. Both the Durston Kakwa 55 and the Outdoor Vitals CS40 Ultra score highly in this category, with buyers praising their durable materials and construction. The Kakwa 55 is noted for its light and durable material, great fabric, and minimal wear and tear, while the CS40 Ultra is commended for its ultra-light but durable fabric and carbon fiber stays. Both packs have a few complaints, but overall, they are seen as highly durable options. This category is a tie as both products offer exceptional durability.

Comfort

Kakwa 55

4.6/ 5.0

CS40 Ultra Backpack

4.4/ 5.0

Comfort is essential for long-distance hiking, as a comfortable pack can make a significant difference in your overall experience. The Durston Kakwa 55 excels in this category with a score of 4.6/5, praised for how well it carries weight, supportive hip belts, and comfortable shoulder straps. Buyers appreciate its stability and how it transfers weight to the hips, making it ideal for thru-hiking. The Outdoor Vitals CS40 Ultra, with a score of 4.4/5, is also comfortable but has slightly more complaints about sore spots and fit issues. The Kakwa 55's superior comfort makes it the winner in this category.

Fit

Kakwa 55

3.8/ 5.0

CS40 Ultra Backpack

3.9/ 5.0

A good fit ensures that the pack stays stable and comfortable on your back, reducing the risk of sore spots and discomfort. Both the Durston Kakwa 55 and the Outdoor Vitals CS40 Ultra score similarly in this category, with the Kakwa 55 at 3.8/5 and the CS40 Ultra at 3.9/5. Buyers appreciate the Kakwa 55's stable ride and contoured shoulder straps, while the CS40 Ultra is noted for its ergonomic design and adjustable shoulder straps. Both packs have some complaints about fit, but overall, they offer a good fit for most hikers. This category is a tie as both products provide a comparable fit.

Accessibility

Kakwa 55

4.4/ 5.0

CS40 Ultra Backpack

4.3/ 5.0

Accessibility refers to how easily you can access your gear while on the move, which is crucial for convenience and efficiency on the trail. Both the Durston Kakwa 55 and the Outdoor Vitals CS40 Ultra score highly in this category, with the Kakwa 55 at 4.4/5 and the CS40 Ultra at 4.3/5. Buyers praise the Kakwa 55 for its easy-to-grab water bottles and generously sized pockets, while the CS40 Ultra is noted for its side pockets and easy-to-reach water bottles. Both packs have some complaints about accessibility, but overall, they offer excellent access to gear. This category is a tie as both products provide excellent accessibility.

Ventilation

Kakwa 55

1.9/ 5.0

CS40 Ultra Backpack

3.2/ 5.0

Ventilation is important for keeping your back cool and dry, especially in hot climates or during intense physical activity. The Outdoor Vitals CS40 Ultra scores higher in this category with a score of 3.2/5, while the Durston Kakwa 55 scores 1.9/5. Buyers complain about the Kakwa 55's lack of ventilation, noting that it can make your back sweaty. The CS40 Ultra, while not perfect, offers better ventilation with its back panels designed to provide some breathing. The CS40 Ultra is the winner in this category due to its superior ventilation.

Water Resistance

Kakwa 55

2.6/ 5.0

CS40 Ultra Backpack

4.1/ 5.0

Water resistance is crucial for keeping your gear dry in wet conditions, which is essential for any outdoor adventure. The Outdoor Vitals CS40 Ultra scores significantly higher in this category with a score of 4.1/5, while the Durston Kakwa 55 scores 2.6/5. Buyers praise the CS40 Ultra for its ultralight waterproof fabric and waterproof properties, while the Kakwa 55 is criticized for not being fully waterproof and leaking in heavy rain. The CS40 Ultra is the clear winner in this category due to its superior water resistance.

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Conclusion & Final Verdict:

In conclusion, the Durston Kakwa 55 and the Outdoor Vitals CS40 Ultra are both excellent ultralight backpacks, but they cater to slightly different needs. The Kakwa 55 is the better choice for thru-hikers who prioritize comfort and trail access, while the CS40 Ultra is ideal for those who need balanced durability and better weather resistance. If you're planning long-distance hikes and need a pack that offers exceptional comfort, the Durston Kakwa 55 is the way to go. However, if you need a pack that can handle various weather conditions and offers better ventilation, the Outdoor Vitals CS40 Ultra is the better option.

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