8-261 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90261, an AS568-261 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 6.734 in (171.04 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 7.012 in (178.1 mm). A back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

As a material, Buna-N (Nitrile) delivers low compression set under sustained load and an economical choice for high-volume maintenance programs. The material holds up against greases and lubricants, petroleum-based oils, and hydraulic fluids. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service. Exposure to ketones or strong acids will shorten service life.

It sees regular use in general industrial maintenance, automotive, and agricultural equipment.

Reference part number HB90261 when ordering; the item is sold individually. Unit weight is approximately 2.5137 g and nominal inside diameter is listed as 6 3/4 inch. Check the compound against your process media, pressure and temperature before committing to a design. APG can cross-reference from an existing part number, a drawing or a physical sample if this size is not an exact match.