8-249 BLACK BUNA 90D BACK-UP RING

Part number HB90249 is an AS568-249 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 4.859 in (123.42 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 5.137 in (130.48 mm). A back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

Buna-N (Nitrile) is widely chosen for the most widely specified general-purpose sealing elastomer, reliable performance in both static and dynamic service. It resists hydraulic fluids, propane and butane, and water. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). It is not the right choice where ozone and direct sunlight or polar solvents are present.

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

HB90249 ships individually. Unit weight is approximately 1.8313 g. Check the compound against your process media, pressure and temperature before committing to a design. For a size or compound outside the standard catalog, APG can quote from a print or sample.