8-351 BLACK BUNA 90D BACK-UP RING

Part number HB90351 is an AS568-351 black Buna-N (Nitrile) 90 Shore A Back-Up Ring built to an inside diameter of 4.725 in (120.02 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 5.145 in (130.68 mm). A back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

As a material, Buna-N (Nitrile) delivers an economical choice for high-volume maintenance programs and low compression set under sustained load. It resists water, petroleum-based oils, and greases and lubricants. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service.

It sees regular use in construction equipment, hydraulic and pneumatic systems, and fluid power.

Stocked as HB90351 and sold individually. Unit weight is approximately 4.1674 g and nominal inside diameter is listed as 4 3/4 inch. Application requirements vary, so validate compatibility with your process conditions prior to 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.