A metal O-ring seal is a high-performance, resilient static sealing element constructed from high-strength metallic tubing or solid wire that is formed into a circular or custom shape and joined by high-integrity welding. These seals are specifically engineered to provide a secure barrier for gases and liquids in extreme operating environments where conventional elastomeric seals would fail due to excessive temperature, pressure, radiation, or corrosive attack.

While O-rings are categorized as resilient seals, they typically undergo significant plastic deformation upon installation, meaning they exhibit minimal springback (generally 2% to 6% of their original cross-section) and are usually discarded after a single use. Plain (Standard/Non-Vented) Metal O-rings are perfectly closed tubes used for lower pressure ranges.