8-430 BLACK BUNA 90D BACK-UP RING

The HB90430 is an AS568-430 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 5.1 in (129.54 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 5.65 in (143.51 mm). This back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

Buna-N (Nitrile) delivers reliable performance in both static and dynamic service, low compression set under sustained load. Expect good resistance to petroleum-based oils, hydraulic fluids, and propane and butane. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). It should not be specified for service in automotive brake fluid or ozone and direct sunlight.

Maintenance and OEM teams specify it across construction equipment, general industrial maintenance, and automotive.

Reference part number HB90430 when ordering; the item is sold individually. Unit weight is approximately 9.454 g and nominal inside diameter is listed as 5 1/8 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. For a size or compound outside the standard catalog, APG can quote from a print or sample.