High energy activity requires keeping hydrated the osprey viper 9 hydration pack ensures that you can carry all the required gear and liquid to perform your best the reservoir is accessed via an asymmetric zip for quick and easy refills the reservoir incorporates a unique hydrostatic plate that maintains an anatomical shape but also keeps water pressure high for a smooth delivery of water the viper 9 provides a ventilated foam back panel and harness keep you cool in hot conditions whils