The CamelBak Filter Adapter connects directly to your hydration system, letting you simultaneously filter water and fill your CamelBak reservoir without even removing your pack. It couldn't make filtration any easier. Here's how it works: You're at a water source and are ready to fill your CamelBak reservoir with water. Remove the bite valve on your CamelBak hose. Insert the larger component (with yellow valve) into the hose. Connect the HydroLink (smaller component) onto most water filter hoses. Snap the HydroLink into the larger component with valve, and reverse-fill your reservoir quickly & conveniently.