4MM CS X 81MM ID BLACK BUNA 70D

Ordered as H4X81, this is a black Buna-N (Nitrile) 70 Shore A O-Ring measuring an inside diameter of 81 mm (3.189 in), a cross section of 4 mm (0.157 in), and an outside diameter of 89 mm (3.5 in). The o-ring seats in a machined groove and forms a leak-tight barrier when compressed between two mating surfaces.

This material stands up to propane and butane, petroleum-based oils, and greases and lubricants. That behavior comes from the compound itself: Buna-N (Nitrile) is known for low compression set under sustained load, reliable performance in both static and dynamic service. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). Exposure to ketones or strong acids will shorten service life.

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

Reference part number H4X81 when ordering; the item is sold individually. Unit weight is approximately 4.098 g. Check the compound against your process media, pressure and temperature before committing to a design. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.