The ADC Professional Daignostic Mercurial Sphygmomanometer features include: Rugged die cast aluminum housing with textured black baked enamel finish. Graduated unbreakable plastic cartridge tube features 4.00mm inside bore for unrestricted, friction-free mercury flow.  High visibility red graduations.  Fold-down cover with spring lock mechanism.  Filter system keeps mercury clean for reliable performance.  Locking reservoir secures mercury during storage, transport, or maintenance. Latex inflation bulb fitted with filter screen end valve reduces dust build-up. Adflow chrome-plated brass air release valve.  Adcuff black nylon cuff with ADC’s proprietary Size Guide marking system prevents mis-cuffing.  Dip molded latex inflation bladder withstands heavy use. Lifetime warranty on cartridge tube.