3/16" Thick, Round Cross Section, Shore 65 - 75, -40 to 250°F Buna-N, also known as nitrile rubber (NBR), is made of a synthetic rubber that has anti-microbial properties and is resistant to chemicals, oils, solvents, greases and petroleum-based fluids. It is resistant to abrasions, cuts, punctures, slashes and snags.|Round cross-section shapes can be used in both static and dynamic applications. They are used as a mechanical seal or gasket and are seated in a groove and compressed during assembly between two or more parts.