8-211 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90211, an AS568-211 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 0.796 in (20.22 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 1.074 in (27.28 mm). A back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

Buna-N (Nitrile) is specified here for strong abrasion and tear resistance, economical choice for high-volume maintenance programs. Expect good resistance to many alcohols, petroleum-based oils, and hydraulic fluids. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). It should not be specified for service in ketones or ozone and direct sunlight.

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

Order part number HB90211, sold individually. Unit weight is approximately 0.348 g. Check the compound against your process media, pressure and temperature before committing to a design. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.