8-358 BLACK BUNA 90D BACK-UP RING

HB90358 is an AS568-358 black Buna-N (Nitrile) 90 Shore A Back-Up Ring measuring an inside diameter of 5.6 in (142.24 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 6.02 in (152.91 mm). In service, this back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

Expect good resistance to water, hydraulic fluids, and petroleum-based oils. That behavior comes from the compound itself: Buna-N (Nitrile) delivers strong abrasion and tear resistance, an economical choice for high-volume maintenance programs. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). Verify compatibility before use with polar solvents or ketones.

Maintenance and OEM teams specify it across general industrial maintenance, agricultural equipment, and automotive.

HB90358 ships individually. Unit weight is approximately 4.9047 g. Review your operating media and conditions against this specification before installation. 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.