This is the slim king of hydration backpacks that carries a big tanker of hydration for the extreme races. The OUTLANDER 4 is geared-up with a 3.0 liter Elite hydration bladder with a Slide-Seal top for easier filling. The pack is designed with our award winning No Dancing Monkey™ 4-point harness system that almost glues the pack on your back and makes it 100% bounce free in action.