... and ROHS approved.4. Various materials and hardness for your option, including Buna-N (NBR), HNBR, VITON, Silicone, FluoroSilicone, EPDM, Teflon, Natural Rubber, BUTYL ... in terms of quantity, quality and convenience for maintenance engineers. They contain either metric size 'O' rings, inch size 'O' rings, or 'O' ring ...