O-rings provide a pressure and fluid seal between cylindrically shaped, overlapping mating surfaces and are most commonly seen in engines, faucets, flanges, valves and cylinders of various sorts.EPDM has superior resistance to weathering, ozone and UV exposure as well as excellent chemical resistance and good electrical properties. It also resists animal and vegetable oils, steam, water and oxygenated solvents. This material meets ASTM D-2000-2BA specifications. Round O-rings are an economical and universally available choice.