8-256 BLACK BUNA 90D BACK-UP RING

Ordered as HB90256, this is an AS568-256 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 5.734 in (145.64 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.012 in (152.7 mm). The back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

Buna-N (Nitrile) is valued for low compression set under sustained load and the most widely specified general-purpose sealing elastomer. This material stands up to many alcohols, water, and petroleum-based oils. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service. Exposure to ketones or polar solvents will shorten service life.

You will find this material specified across automotive, general industrial maintenance, and agricultural equipment.

Reference part number HB90256 when ordering; the item is sold individually. Unit weight is approximately 2.0933 g and nominal inside diameter is listed as 5 3/4 inch. As always, verify media compatibility and operating conditions against the requirements of your specific application. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.