The Katadyn Quick Fill Hydration Adaptor Accessory is a H2O filter accessory that guarantees every drop of H2O you pump makes it into your hydration pack. You can attach any H2O filter with an output hose to any hydration pack bladder by the external drink hose or the quick release fitting on the bladder. The Katadyn Quick Fill Hydration Adaptor Accessory ensures your pack bladder is filled without soaking everything else in the pack.