8-129 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90129, an AS568-129 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 1.549 in (39.34 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 1.755 in (44.58 mm). A back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

Expect good resistance to hydraulic fluids, water, and greases and lubricants. Buna-N (Nitrile) is widely chosen for strong abrasion and tear resistance, the most widely specified general-purpose sealing elastomer. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C).

Maintenance and OEM teams specify it across general industrial maintenance, agricultural equipment, and fluid power.

Order part number HB90129, sold individually. Unit weight is approximately 0.465 g and nominal inside diameter is listed as 1 9/16 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.