8-121 BLACK BUNA 90D BACK-UP RING

This back-up ring is supplied in AS568-121 black Buna-N (Nitrile) 90 Shore A measuring an inside diameter of 1.049 in (26.64 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 1.255 in (31.88 mm), catalogued under part number HB90121. It allows a standard o-ring to operate at higher pressures than it could unsupported.

The material holds up against petroleum-based oils, greases and lubricants, and many alcohols. That behavior comes from the compound itself: Buna-N (Nitrile) is known 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 automotive brake fluid or strong acids.

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

Stocked as HB90121 and sold individually. Unit weight is approximately 0.3245 g and nominal inside diameter is listed as 1 1/16 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.