A 2 litre Tpu bladder sits in the main sleeve of this 8 litre pack, enough water for a half day on foot or a long ride without stopping to refill. Four separate measures guard against leaking, namely an automatic shut-off valve, an upgraded rubber sealing ring, securing straps and a full airtight test on every unit before it ships, so a pack riding against the back stays dry. The bladder fills through a wide opening that a hand fits into for cleaning and for adding ice. Shell fabric is 420D polyester with a waterproof finish, light enough that the empty pack weighs only 1.10 pounds yet tough enough for scrub and rock contact. An elastic storage cord across the face holds a jacket, an umbrella or a towel outside the main compartment. Overall size is 18.11 by 12.60 by 4.92 inches. Hand wash the shell and rinse the bladder after each use.