8-277 BLACK BUNA 90D BACK-UP RING

Part number HB90277 is an AS568-277 black Buna-N (Nitrile) 90 Shore A Back-Up Ring supplied with an inside diameter of 11.484 in (291.69 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 11.762 in (298.75 mm). A back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

It resists greases and lubricants, hydraulic fluids, and propane and butane. That behavior comes from the compound itself: Buna-N (Nitrile) is valued for low compression set under sustained load, strong abrasion and tear resistance. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). It is not the right choice where ketones or ozone and direct sunlight are present.

You will find this material specified across automotive, agricultural equipment, and fluid power.

Order part number HB90277, sold individually. Unit weight is approximately 4.2036 g and nominal inside diameter is listed as 11 1/2 inch. Check the compound against your process media, pressure and temperature before committing to a design. APG can cross-reference from an existing part number, a drawing or a physical sample if this size is not an exact match.