8-445 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90445, an AS568-445 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 7.975 in (202.57 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 8.525 in (216.54 mm). A back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

The material holds up against propane and butane, hydraulic fluids, and petroleum-based oils. That behavior comes from the compound itself: Buna-N (Nitrile) is widely chosen for reliable performance in both static and dynamic service, the most widely specified general-purpose sealing elastomer. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). Applications involving automotive brake fluid or ozone and direct sunlight call for a different compound.

You will find this material specified across automotive, hydraulic and pneumatic systems, and agricultural equipment.

This item is sold individually under part number HB90445. Unit weight is approximately 14.27 g. Review your operating media and conditions against this specification before installation. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.