... ..Electronic profession seal or rubber components, like in handset pressed key, in DVD antirattler, electric cable wire connection seal and so ... hardness for your option, including Buna-N (NBR), HNBR, VITON, Silicone, FluoroSilicone, EPDM, Teflon, Natural Rubber, BUTYL, SBR, Neoprene, HYPALON, ... DVGW certification and British WRAS (WRC) drinking water standard certification. Silicone Rubber O-Ring