8-279 BLACK BUNA 90D BACK-UP RING

The HB90279 is an AS568-279 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 12.984 in (329.79 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 13.262 in (336.85 mm). This back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

The material holds up against many alcohols, propane and butane, and water. That behavior comes from the compound itself: Buna-N (Nitrile) offers strong abrasion and tear resistance, an economical choice for high-volume maintenance programs. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). It should not be specified for service in strong acids or automotive brake fluid.

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

Reference part number HB90279 when ordering; the item is sold individually. Unit weight is approximately 4.7222 g. As always, verify media compatibility and operating conditions against the requirements of your specific application.