UltrAspire describes the Zygos Hydration Vest as, the most human compatible vest system ever built, which is pretty sweet, even if describing it as human compatible makes it seem like most other vests were designed to be worn by robots or dogs. What UltrAspire is trying to say is that Zygos is one of the most ergonomic, comfortable, and thoughtfully designed large volume hydration packs out there, perfect for hiking, biking, and long distance running. It sits on your back incredibly comfortably, thanks to the breathable and highly elastic Max 02 sternum strap, compression straps, and comfortable wrap around hip belt. Once it's snug, the straps won't loosen up on you, while the nylon and mesh construction will help you stay cool during high output activities. Like any good hydration pack, the Zygos has both a hanging 2L reservoir and dual front bottle holsters, along with a multitude of stash pockets on the front, sides, and back to keep your snacks, gels, and other key gear handy.