Gear editor Gus Alexandropoulos talks about the Osprey Viper 13. The hydration pack is perfect for long trail rides. It has plenty of pockets including three outer mesh pouches and a small upper pocket for your cellphone and wallet. The total carrying capacity is 13 l. Three of those litres can be taken up with water in the hydration bladder. It’s made of stiff plastic so it retains it shape, making it more comfortable against your back. The bladder has a large opening for filling and cleaning. The bite valve has a magnet that attaches it to the chest strap to keep everything from flapping around as you bounce down singletrack. For apres-ride, hang your helmet from the “LidLock,” a clip at the top of the pack.