An O-ring is a mechanical gasket in the shape of an "O" with a circular cross-section used to seal connections between two or more parts. Also called packing joints, o-rings are commonly found in machine design as they are inexpensive and simple to use while still offering a reliable seal. Shop our huge selection of O-rings in a large variety materials including: Buna N (Nitrile), Chloroprene (Neoprene), Ethylene Propylene, Flurocarbon (Viton), Flurosilicone, Hydrogenated Nitrile and Silicon. With sizes ranging from #1 to #392 you're sure to find the right fit for your air conditioner or plumbing job. For more information on chemical compatibilities, view our Chemical Compatibility Table.