-421 BLACK BUNA 90D O-RING

Part number H90421 is an AS568-421 black Buna-N (Nitrile) 90 Shore A O-Ring supplied with an inside diameter of 3.975 in (100.97 mm), a cross section of 0.275 in (6.99 mm), and an outside diameter of 4.525 in (114.94 mm). An o-ring seats in a machined groove and forms a leak-tight barrier when compressed between two mating surfaces.

As a material, Buna-N (Nitrile) is valued for strong abrasion and tear resistance, low compression set under sustained load. The material holds up against petroleum-based oils, greases and lubricants, and many alcohols. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). Applications involving ozone and direct sunlight or ketones call for a different compound.

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

Stocked as H90421 and sold individually. Unit weight is approximately 17.29 g. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.