UltrAspire Zygos 4.0 Hydration Pack。Since the first iteration of the Zygos, tens of thousands of runners have utilized this high-capacity 14 liter race vest. The lightweight and comfortable wrap around design complimented by the ErgoFit Harness ensures the Zygos 5.0 will be stable, comfortable, and hindrance free. The pack\'s MaxO2 Form adjustable closure system secures and adapts to the pack\'s load. This innovative system can conform the pack to the body using a single pull. Similar to the MaxO2 Sternum, this system allows the pack to remain secured without impeding natural breathing. Featuring 8 on-the-go pockets there are 2 zippered shoulder pockets, a dual 4-way stretch mesh pocket, a pair of stretch mesh pockets (one of which is zippered and suitable for carrying a large cell phone), a zippered side pocket, and a magnetically closed side pocket. The main back compartment has been reinforced at the stress points with XT fabric which contains stronger than steel ripstop fibers. This pack includes a 2-liter reservoir that fits into the removable insulated bladder compartment.