8-371 BLACK BUNA 90D BACK-UP RING

HB90371 is an AS568-371 black Buna-N (Nitrile) 90 Shore A Back-Up Ring built to an inside diameter of 8.475 in (215.27 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 8.895 in (225.93 mm). In service, this back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

Buna-N (Nitrile) is known for reliable performance in both static and dynamic service, strong abrasion and tear resistance. The material holds up against hydraulic fluids, greases and lubricants, and water. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). It should not be specified for service in automotive brake fluid or ozone and direct sunlight.

It sees regular use in agricultural equipment, automotive, and hydraulic and pneumatic systems.

Order part number HB90371, sold individually. Unit weight is approximately 7.169 g and nominal inside diameter is listed as 8 1/2 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.