8-440 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90440, an AS568-440 black Buna-N (Nitrile) 90 Shore A Back-Up Ring supplied with an inside diameter of 6.725 in (170.82 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 7.275 in (184.79 mm). A back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

This material stands up to petroleum-based oils, propane and butane, and water. Buna-N (Nitrile) is valued for strong abrasion and tear resistance, the most widely specified general-purpose sealing elastomer. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). Verify compatibility before use with polar solvents or ozone and direct sunlight.

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

Stocked as HB90440 and sold individually. Unit weight is approximately 11.856 g and nominal inside diameter is listed as 6 3/4 inch. Check the compound against your process media, pressure and temperature before committing to a design. 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.