Bel-Art Check Valves; &frac14; to  in. Tapered End Diameter, Polypropylene (Pack of 6) (H19716-0000) Economical and highly chemical resistant; these polypropylene check valves can handle vacuum lines and other flexible tubings Autoclavable; it help to stop backflow damage when pressure is interrupted or vacuum is broken All non-metallic wetted surfaces Tapered barbed connections in three sizes 2-3/8" overall length, 3/4" length tapered end, 1/4 to 3/8" in and out diameter tapered end