8-270 BLACK BUNA 90D BACK-UP RING

This back-up ring is supplied in AS568-270 black Buna-N (Nitrile) 90 Shore A measuring an inside diameter of 8.984 in (228.19 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 9.262 in (235.25 mm), catalogued under part number HB90270. It extends o-ring service life by supporting the seal against extrusion under high pressure.

Expect good resistance to petroleum-based oils, water, and many alcohols. That behavior comes from the compound itself: Buna-N (Nitrile) is known for an economical choice for high-volume maintenance programs and low compression set under sustained load. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service. It is not the right choice where polar solvents or automotive brake fluid are present.

You will find this material specified across automotive, hydraulic and pneumatic systems, and agricultural equipment.

Reference part number HB90270 when ordering; the item is sold individually. Unit weight is approximately 3.332 g and nominal inside diameter is listed as 9 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.