8-348 BLACK BUNA 90D BACK-UP RING

This back-up ring is supplied in AS568-348 black Buna-N (Nitrile) 90 Shore A measuring an inside diameter of 4.35 in (110.49 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 4.77 in (121.16 mm), catalogued under part number HB90348. It installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

The compound resists greases and lubricants, petroleum-based oils, and water. Buna-N (Nitrile) offers low compression set under sustained load, reliable performance in both static and dynamic service. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). Verify compatibility before use with ketones or automotive brake fluid.

Typical settings include agricultural equipment, construction equipment, and fluid power.

Reference part number HB90348 when ordering; the item is sold individually. Unit weight is approximately 4.038 g and nominal inside diameter is listed as 4 3/8 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.