8-242 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90242, an AS568-242 black Buna-N (Nitrile) 90 Shore A Back-Up Ring built to an inside diameter of 3.984 in (101.19 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 4.262 in (108.25 mm). A back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

The compound resists greases and lubricants, propane and butane, and petroleum-based oils. Buna-N (Nitrile) is valued for strong abrasion and tear resistance, an economical choice for high-volume maintenance programs. Service temperature is rated from -40°F (-40°C) through 250°F (121.1°C). Verify compatibility before use with ketones or automotive brake fluid.

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

This item is sold individually under part number HB90242. Unit weight is approximately 1.471 g and nominal inside diameter is listed as 4 inch. Review your operating media and conditions against this specification before installation. For a size or compound outside the standard catalog, APG can quote from a print or sample.