Fill your hydration pack reservoir directly from your screw on/off filter without removing it from your backpack with the Sawyer Fast Fill Adapter (hydration pack and filter sold separately). This handy Sawyer "hack" makes refilling hassle free. Adapters attach directly to the drinking tube on most hydration reservoirs. Designed for use with industry standard 1/4-inch inner diameter tubing, it's compatible with the Sawyer Squeeze Filters (models SP129, SP131, SP181, SP182, and SP137) and Sawyer MINI Filter (model SP128 and other colors).