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January 22, 2015 Comments (1) Gear Reviews

UltrAspire Zygos – Gear Review

UltrAspire made a splash in 2013 with the award winning Alpha hydration vest. If you’re a fan of the Alpha you are going to love the Zygos, which hits the shelves in 2015. The Zygos has the same template and shape as the Alpha, but has added capacity for longer adventures. With a 14L carrying capacity I initially thought this would be a vest that I would only use on really long adventure runs, but ever since my first test run I have found myself using it more frequently because it rides so well, is very comfortable and provides easy access to all of my essentials. It has quickly become my go to vest for almost all of my intermediate and longer runs.

Zygos specs:

  • Patent-pending Max O2 Sternum attachment system
  • 2X zippered wrap-around side pockets for on the go access
  • Internal small zippered pocket for keys, lip balm and other essentials
  • Adjustable compression straps to hold a fully-outfitted pack stable and secure
  • Lighter weight front pocket mesh fabric
  • Includes a 2L bladder
  • 14L of gear carrying capacity
  • Electrolyte pill pocket
  • Hook and strap for ice axe
  • Two draw-string mesh pockets on each chest strap (Can hold water bottles)
UltrAspire Zygos

UltrAspire Zygos


Our male and female testers put the Zygos through a wide range of conditions and terrain to get the best possible test results. It was used on multiple 10-20 mile runs including one tester that used it on a 27 hour self-supported ultra adventure that covered 20+ rugged peaks in the Wasatch Mountains.

Fit & Comfort- 4.0

The new Max O2 sternum attachment system is designed to allow uninhibited breathing. Unlike most current hydration vests that use straps that will not expand, the new Max O2 system expands and contracts with your lungs, but still keeps the pack tight to your body without moving around. It is very comfortable and seems to work very well as designed, however one of our testers had issues keeping the cords from getting loose.


“The closing bungee straps were inefficient and kept loosening, particularly when the route required scrambling”


Another tester however, really liked the new system:

“The elastic cord sternum straps were flexible, comfortable and very snug on my body.”


The overall fit and comfort of the pack is excellent. The materials are light, soft and it remains comfortable even after hours of running. UltrAspire nailed it with the weight distribution. Even when the pack was fully loaded it did not bounce around and held snug, while still staying comfortable – pretty incredible given the storage capacity of the vest.


“Weight wise it felt like no matter what I crammed in there it didn’t feel any different and I didn’t notice the additional weight after the initial items were packed because the vest distributed weight well.”


Ready to roll

Ready to roll


Storage Capacity- 5.0

The storage capacity is what our testers loved most about this vest. There are several spacious compartments and the storage space allows you to carry just about anything that you will need for long adventure runs.


“I was impressed that I could fit all the items I needed for a self-supported 27 hour adventure run comfortably with room to spare. It stored everything I wanted to bring, and some of my other vests couldn’t hold half of that stuff.”


The storage capacity of the vest approaches that of a lot of fast packs, but the remarkable thing is it still feels and rides like a much smaller pack.


Plenty for a big adventure

Plenty for a big adventure


Ease of Access- 5.0

It was obvious to our testers that the vest was very well designed from an access perspective. The large mesh pockets in front allow you to hold gels, cell phones and extra water bottles. There is also an electrolyte pill pocket and a zipper elastic mesh pocket for storing smaller items like lip balm or sunscreen.


“With the amount of pockets and compartments in the front of the vest, I was able to run up to 20 miles without ever having to take the vest off. I was able to store all of my gels, salt pills and my camera and they were all easy to get to on the run”


The vest also features large side pockets on both sides that wrap around the vest and can easily be accessed without taking off the vest. These pockets are large enough to store extra food, gels, wallets, headlamps or cell phones.

Overall the compartments are very easy to access even on the run. All of the testers were very satisfied and felt that the vest was very well designed.



Fully Loaded


 Reservoir and Valves- 4.0

The pack comes standard with a 2L bladder with the UltrAspire infusion valve, optimized for high flow rate drinking and a large diameter hose that delivers more water to the valve. There is an isolated pocket for the bladder on the back of the pack. The pack also has two mesh pockets in the front of the vest that can be used to carry a water bottle. The one complaint that we heard from our testers was the bite valve was hard to get open.


“The bite valve was annoying and I had to open it with my hands because I had to bite down really hard to get any water.”


Summiting Devils Castle wearing the UltrAspire Zygos

Summiting Devils Castle wearing the UltrAspire Zygos

Quality- 4.0

Most of the pack is made with a very light water-proof nylon. The shoulder straps on the front of the pack are mesh with larger openings than previous UltrAspire packs. After a month of testing in very rugged terrain the pack still looks brand new other than a very small tear in the main compartment on the back which was easily repaired.


Ready to roll

Ready to roll

Overall- 4.4

Overall our testers were very pleased with this pack in terms of capacity and comfort. It has the ride and feel of a pack with a much smaller capacity, while at the same time providing a snug fit. The pack is also very versatile. It can be used for shorter runs as well as long ultra adventure runs.


“I have owned several hydration packs and after a month of testing the Zygos has become the favorite in my arsenal. I love the versatility and comfort and would highly recommend it.”


Zygos on the WURL

Zygos on the WURL

One Response to UltrAspire Zygos – Gear Review

  1. Paul says:

    Thx for the review – sounds like an awesome and very versatile pack! Capacity wise the UltrAspire Omega would actually fit my bill 99% of the times when I’m on longer, self supported outings and/ or in case I need to carry a mandatory kit. On the other hand the Zygos may be a very nice daypack when out cycling or hiking with my boys.

    I *am* intrigued by the new max o2 sternum strap, too, so I wonder just how much the Zygos can be cinched down without completely losing form/ fit … Haven’t found any images with the pack minimally loaded so I was wondering what your experience was when carrying it only lightly packed.

    Thx for a brief reply!
    Best from Berlin, Germany

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