8-011 BLACK BUNA 90D BACK-UP RING

HB90011 is an AS568-011 black Buna-N (Nitrile) 90 Shore A Back-Up Ring measuring an inside diameter of 0.301 in (7.65 mm), a cross section of 0.07 in (1.78 mm), and an outside diameter of 0.441 in (11.2 mm). In service, this back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

It resists many alcohols, water, and petroleum-based oils. That behavior comes from the compound itself: Buna-N (Nitrile) is widely chosen for low compression set under sustained load, strong abrasion and tear resistance. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). Verify compatibility before use with ketones or strong acids.

Maintenance and OEM teams specify it across agricultural equipment, fluid power, and hydraulic and pneumatic systems.

HB90011 ships individually. Unit weight is approximately 0.066 g and nominal inside diameter is listed as 5/16 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.