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Sold Out Item # USP1C201M

UltrAspire Zygos 4.0 Hydration Running Vest

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UltrAspire Zygos 4.0 Hydration Running Vest

By Steven

Enwild Gear Specialist

The Enwild Difference

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A great option for ultra racing, the UltrAspire Zygos 4.0 running vest has ample storage capacity for hydration and other race-day needs. It offers excellent all-day fit and includes a 2L hydration system.


A great option for ultra racing, the UltrAspire Zygos 4.0 running vest has ample storage capacity for hydration and other race-day needs. It offers excellent all-day fit and includes a 2L hydration system.

The broad, honey-combed mesh fabric of the pack maximizes breathability and next-to-skin comfort. Soft perimeter fabrics further enhance comfort. To ensure an appropriate fit, the pack is available in Small (best fits chest sizes of 30"-36”), Medium (32"-38"), and Large (34”-40”) size options. Dual hook-and-pull chest straps allow you to fine tune fit and eliminate “bounce”.

A large pocket on the back of the pack houses the included 2L hydration system. A broad opening and simple hanging system make it easy to get the reservoir in and out of the pocket. Adding convenience, the drinking tube can easily be run over either shoulder.

In addition to the large rear compartment, other pockets include a large rear stretch shove-it pocket, and two zippered stretch lateral pockets that are positioned to allow convenient on-the-go access. Two large mesh pockets on the front harness are capable of comfortably stowing water bottles (not included). Other harness pockets include a small zippered pocket and a water-resistant magnet-closure pocket that is perfect for stowing electrolytes. Additional features include rear crossover compression straps, trekking pole attachments loops.

The UltrAspire Zygos 4.0 running vest is available in your choice of size and color options.

  • 854 cubic inches (14 liters) of storage
  • Sweatproof webbing
  • Magnon pocket
  • 30 denier HD ripstop nylon construction
  • Ultracool system includes lightweight mesh and small footprint to reduce contact and increase cooling
  • Insulated pouch
  • MaxO2 Sternum buckle system to keep the Epic XT secure while the upper body moves
  • Comfortable wraparound style with full compression
  • Includes a 2-liter reservoir with magnetic clip

Technical Specs

Best Use
Panel Loading
Fits Torso
Small: 30"-36" chest measurement (widest point)
Medium: 32"-38" chest measurement (widest point)
Large: 34"-42" chest measurement (widest point)
Hydration Compatible
Yes; 2L hydration system included
Sternum Strap
Yes; Two adjustable
Torso Adjustment
854 cu in
Limited Lifetime
Hydration Running Vest
Silicone and PU-coated nylon
Item Weight
16.o oz w/ reservoir

3 Reviews

4.67 / 5


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Love it!


It’s so lightweight with so much space for storage! This is perfect for trail running and long hikes on incline when you want to remain light. The extra pockets on the front and sides are perfect. Love everything about this pack. No chaffing either.



John D.


Great Ultra Pack - I've put every Zygos version to the test


The Zygos line has been my ultramarathon and general lightweight running pack for years. I still have my Zygos 1.0 and 2.0 and needed something with a bit more storage for my latest Nolan’s 14 attempt, but not as big as my Epic pack, which I use for the 20+ hour legs. The Zygos 4.0 was awesome. The waist and front pocket storage is meaningfully more that the 1.0 and 2.0 versions and it’s still super light and comfortable. I have a thing about stuffing too much into pockets and get frustrated trying to find various food items I want. Having the 4 pockets on the front help me organize and know where my various items are, so i can grab them efficiently. I like the slightly lower hose clip location on the left chest, compared to the other models. As with the Zygos 2.0, the ability to stash and retrieve z-poles without taking the pack off is appreciated. And, as with all UltAspire packs, I have NEVER had a material failure or other quality issue. I’ve had multiple friends with other brand packs have zippers fail and that’s just not acceptable during an ultramarathon, high alpine mountain adventure, or just a long run.


The main compartment is mesh, so has zero water resistance, unlike the 1.0 or 2.0. The capacity of the main compartment is not significantly more than the Zygos 1.0 or 2.0

Erik W.


So Far So Great


Excellent weight balance, front to back. Secure fit. Tons of pockets. Lots of space.


Sternum straps are thin elastic which sometime loosen. I'm also worried about their longevity, given the material.