8-048 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90048, an AS568-048 black Buna-N (Nitrile) 90 Shore A Back-Up Ring supplied with an inside diameter of 4.739 in (120.37 mm), a cross section of 0.07 in (1.78 mm), and an outside diameter of 4.879 in (123.93 mm). A back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

This material stands up to greases and lubricants, water, and many alcohols. That behavior comes from the compound itself: Buna-N (Nitrile) is known for strong abrasion and tear resistance, 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 strong acids are present.

Maintenance and OEM teams specify it across fluid power, general industrial maintenance, and construction equipment.

Order part number HB90048, sold individually. Unit weight is approximately 0.828 g. As always, verify media compatibility and operating conditions against the requirements of your specific application. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.