5.7MM CS X 389.3MM ID BLACK BUNA 70D

Ordered as H5.7X389.3, this is a black Buna-N (Nitrile) 70 Shore A O-Ring built to an inside diameter of 389.3 mm (15.327 in), a cross section of 5.7 mm (0.224 in), and an outside diameter of 400.7 mm (15.78 in). The o-ring creates a positive seal at flange, piston and rod interfaces without added hardware. This item is further identified as Metric O-RING, JIS G390.

The material holds up against greases and lubricants, petroleum-based oils, and many alcohols. That behavior comes from the compound itself: Buna-N (Nitrile) is valued for strong abrasion and tear resistance, low compression set under sustained load. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). Applications involving ketones or strong acids call for a different compound.

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

H5.7X389.3 ships individually. Unit weight is approximately 38.948 g. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing.