... and so on.4.All rubber products are made according to international standard: ISO 3601, AS 568A, DIN3771, JIS B2401.5. Our products ... your option, including Buna-N (NBR), HNBR, VITON, Silicone, FluoroSilicone, EPDM, Teflon, Natural Rubber, BUTYL, SBR, Neoprene, HYPALON, etc.7.we received ... NSF, Germany DVGW certification and British WRAS (WRC) drinking water standard certification. Silicone O-Ring