8-258 BLACK BUNA 90D BACK-UP RING

HB90258 is an AS568-258 black Buna-N (Nitrile) 90 Shore A Back-Up Ring built to an inside diameter of 5.984 in (151.99 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.262 in (159.05 mm). In service, this back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

The compound resists propane and butane, greases and lubricants, and water. That behavior comes from the compound itself: Buna-N (Nitrile) is valued for strong abrasion and tear resistance, an economical choice for high-volume maintenance programs. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service. Applications involving automotive brake fluid or polar solvents call for a different compound.

You will find this material specified across automotive, hydraulic and pneumatic systems, and fluid power.

Reference part number HB90258 when ordering; the item is sold individually. Unit weight is approximately 2.2588 g and nominal inside diameter is listed as 6 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.