O2 Check Valve Riser - DISS (for operatory) O2 Check Valve Riser - DISS (for operatory) 23173-FRU Use for pre-installation of Digital Ultraâ„¢ Flushmount and Ultra PCâ„¢ % Cabinet Mount flowmeters. Includes 28085 (O2 DISS x DISS Demand Check Valve Assembly). Where to Buy x Category - Any - Dealer Partners Sales Representative Strategic Markets Schools Representative Accutronâ„¢ Equipment Sales Zip Code Find Representative Reset No results found. Please try a different search or explore: Sales Representatives | Dealer Partners | Strategic Markets | Schools | Accutron