Rancilio Manual Group Feeding Valve Piston Gasket (PTFE) Small PTFE gasket that seals the piston inside Rancilio's manual group feeding valve. SPECIFICATIONS Size: 12mm OD x 9mm ID x 1mm thick Material: PTFE COMPATIBILITY Fits: Rancilio manual brew group feeding valve piston INSTALLATION Simple gasket replacement for anyone who has already opened the feeding valve for service. PRO TIPS PTFE won't compress-set like rubber, so a worn gasket here usually shows up as a slow drip or weeping around the valve piston rather than a sudden leak, replace at the first sign of seepage before it scores the piston bore.