8-168 BLACK BUNA 90D BACK-UP RING

Ordered as HB90168, this is an AS568-168 black Buna-N (Nitrile) 90 Shore A Back-Up Ring built to an inside diameter of 7.237 in (183.82 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 7.443 in (189.05 mm). The back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

Expect good resistance to many alcohols, propane and butane, and petroleum-based oils. That behavior comes from the compound itself: Buna-N (Nitrile) is known for strong abrasion and tear resistance, an economical choice for high-volume maintenance programs. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service.

It sees regular use in construction equipment, general industrial maintenance, and hydraulic and pneumatic systems.

HB90168 ships individually. Unit weight is approximately 2.04 g. As always, verify media compatibility and operating conditions against the requirements of your specific application. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.