8-039 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90039, an AS568-039 black Buna-N (Nitrile) 90 Shore A Back-Up Ring built to an inside diameter of 2.739 in (69.57 mm), a cross section of 0.07 in (1.78 mm), and an outside diameter of 2.879 in (73.13 mm). A back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

Buna-N (Nitrile) delivers an economical choice for high-volume maintenance programs and low compression set under sustained load. This material stands up to petroleum-based oils, hydraulic fluids, and many alcohols. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). Exposure to polar solvents or ozone and direct sunlight will shorten service life.

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

HB90039 ships individually. Unit weight is approximately 0.483 g. Application requirements vary, so validate compatibility with your process conditions prior to installation.