O-rings are circular elastomer sealing elements used to prevent the passage of liquids, gases and dust. Sealing is generally achieved by compressing the O-ring between two surfaces. O-rings are produced from different materials depending on the area of use. These include elastomers such as NBR (Nitrile), FKM (Viton), silicone and EPDM. Each is preferred according to different temperature, chemical resistance and application requirements.