8-393 BLACK BUNA 90D BACK-UP RING

HB90393 is an AS568-393 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 23.94 in (608.08 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 24.36 in (618.74 mm). In service, this back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

It resists propane and butane, water, and petroleum-based oils. Buna-N (Nitrile) is known for reliable performance in both static and dynamic service, low compression set under sustained load. Service temperature is rated from -40°F (-40°C) through 250°F (121.1°C). It is not the right choice where ozone and direct sunlight or strong acids are present.

You will find this material specified across general industrial maintenance, fluid power, and automotive.

Stocked as HB90393 and sold individually. Nominal inside diameter is listed as 24 inch. Review your operating media and conditions against this specification before installation. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.