Reservoir can be removed and filled while leaving the hose threaded through the pack and turned inside-out for easy cleaning. The opening automatically shuts off when the hose is removed. It has a smooth inside for easier cleaning and smoother outside to quickly slip in and out of packs. Top closure is both fold-over and slide-closed, eliminating leaking and opening fully for cleaning. This reservoir utilizes the Hypervalve Hose which incorporates an on/off bite valve and is BPA free.