Hydration Backpack 2.5 Liters. 2.5 Liter Bladder Capacity and 8 Liter Rucksack Compartment Padded back for extra comfort in long hikes or jogs Made From 600D Polyester - Waterproof 46cm (18 inches) x 24cm (9 inches) - weighs 14 oz dry Chest Strap for Superior Comfort and Stability