8-040 BLACK BUNA 90D BACK-UP RING

HB90040 is an AS568-040 black Buna-N (Nitrile) 90 Shore A Back-Up Ring supplied with an inside diameter of 2.864 in (72.75 mm), a cross section of 0.07 in (1.78 mm), and an outside diameter of 3.004 in (76.3 mm). In service, this back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

This material stands up to greases and lubricants, hydraulic fluids, and water. That behavior comes from the compound itself: Buna-N (Nitrile) delivers low compression set under sustained load and the most widely specified general-purpose sealing elastomer. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C).

Typical settings include agricultural equipment, automotive, and fluid power.

Stocked as HB90040 and sold individually. Unit weight is approximately 0.502 g and nominal inside diameter is listed as 2 7/8 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.