The FastBack Double Century Hydration Pack straddles the back of your seat with one three-liter pack on either side. It's the solution for lowracers and other hard-shell bikes & trikes with limited tire clearance, as well as Bacchetta EuroMesh seats. Stow away a 3L CamelBak Hydration Bladder one side and use the other like a pannier to keep some gear. If you ride in the hottest parts of the planet, enjoy bike touring or want to ride and ride without having to stop for a refill, then the FastBack Double Century Hydration Pack is a must have!