8-272 BLACK BUNA 90D BACK-UP RING

This back-up ring is supplied in AS568-272 black Buna-N (Nitrile) 90 Shore A supplied with an inside diameter of 9.484 in (240.89 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 9.762 in (247.95 mm), catalogued under part number HB90272. It allows a standard o-ring to operate at higher pressures than it could unsupported.

The compound resists water, hydraulic fluids, and propane and butane. That behavior comes from the compound itself: Buna-N (Nitrile) is known for reliable performance in both static and dynamic service, the most widely specified general-purpose sealing elastomer. Service temperature is rated from -40°F (-40°C) through 250°F (121.1°C). It should not be specified for service in strong acids or ketones.

Maintenance and OEM teams specify it across automotive, construction equipment, and agricultural equipment.

Reference part number HB90272 when ordering; the item is sold individually. Unit weight is approximately 3.4679 g. Application requirements vary, so validate compatibility with your process conditions prior to installation. For a size or compound outside the standard catalog, APG can quote from a print or sample.