O2 Check Valve Riser - DISS (for operatory) O2 Check Valve Riser - DISS (for operatory) Sign in to save to your list 23173-FRU Use for pre-installation of Digital Ultra™ Flushmount and Ultra PC™ % Cabinet Mount flowmeters. Includes 28085 (O2 DISS x DISS Demand Check Valve Assembly). Where to Buy Ask a specialist