The Back Pack has a capacity of 5 US gallons (19 litres) and is 25"h x 16.5"w (63.5cm x 42cm) when empty. Manufactured from a strong polyester based fabric, protected by a thermoplastic polymer. It has a 4" filling port with a removable debris screen, 3" wide fully padded shoulder straps. Weighs approximately 40lbs. (18.2kg) when full.