Rehydrate on the go with a Thule Vital Hydtration Packs. Whether you run, bike, or hike a Thule Vital will help keep you hydrated. The Vital Series comes in three sizes: 3 Litres, 6 Litres, and 8 Litres. Each hydration pack features the hands-free ReTrakt magnetic hose return system, convenient jersey-style pockets, and lightweight, ventilated materials.