8-391 BLACK BUNA 90D BACK-UP RING

This back-up ring is supplied in AS568-391 black Buna-N (Nitrile) 90 Shore A measuring an inside diameter of 21.953 in (557.61 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 22.373 in (568.27 mm), catalogued under part number HB90391. It allows a standard o-ring to operate at higher pressures than it could unsupported.

Buna-N (Nitrile) is specified here for reliable performance in both static and dynamic service, strong abrasion and tear resistance. This material stands up to water, petroleum-based oils, and many alcohols. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). Verify compatibility before use with strong acids or ozone and direct sunlight.

You will find this material specified across fluid power, automotive, and general industrial maintenance.

Stocked as HB90391 and sold individually. Unit weight is approximately 18.404 g and nominal inside diameter is listed as 22 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing.