Included is an **Osprey Hydraulics 2.0 Liter Hydration Reservoir (70 oz) hydration bladder. It is designed for use with most hydration-compatible backpacks for hiking, biking, and outdoor activities. The reservoir has a wide opening for easy filling and cleaning along with a bite valve for easy drinking. It is made from BPA-free materials and holds up to 2 liters (70 oz) of water. A great replacement or spare hydration bladder for your gear.