The osprey viper 9l hydration pack is a great riding partner carrying your food drink and tools in a safe and organised layout the viper 9l comes supplied with a 3l hydraulics reservoir which is ideal for on the trail hydration 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 osprey have also solved the loose dr