Osprey Transporter 18L Waterproof Roll Top BackpackTransporter 18L Waterproof Roll Top Backpack If your adventure is bound to be wet, the Transporter Waterproof 18 is better than water off a duck's back. Its IPX6 roll top closure keeps the elements out while simple internal organization keeps up to 18 liters of gear inside and in place. We've applied our comfortable AirScape backpanel, giving you a more stable carry. By foot, bike, board or boat, keep your gear dry with our Transporter Waterproof 18.