-257 BLACK BUNA 50D O-RING

Ordered as H50257, this is an AS568-257 black Buna-N (Nitrile) 50 Shore A O-Ring with an inside diameter of 5.859 in (148.82 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.137 in (155.88 mm). The o-ring remains the most cost-effective sealing element available for pressurized assemblies.

The material holds up against many alcohols, greases and lubricants, and water. That behavior comes from the compound itself: Buna-N (Nitrile) is specified for reliable performance in both static and dynamic service, an economical choice for high-volume maintenance programs. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). It is not the right choice where strong acids or ketones are present.

Maintenance and OEM teams specify it across fluid power, construction equipment, and agricultural equipment.

Reference part number H50257 when ordering; the item is sold individually. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing.