568-353 BUNA 70 SQUARE CUT RINGS

APG stocks the SH70353, an AS568-353 black Buna-N (Nitrile) 70 Shore A Square-Cut Ring built to an inside diameter of 4.975 in (126.37 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 5.395 in (137.03 mm). A square-cut ring resists the spiral failure that affects round rings on long reciprocating strokes.

Expect good resistance to propane and butane, greases and lubricants, and hydraulic fluids. That behavior comes from the compound itself: Buna-N (Nitrile) is specified for low compression set under sustained load, strong abrasion and tear resistance. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C). It should not be specified for service in ketones or strong acids. The profile itself contributes a rectangular section that will not roll in the groove and greater resistance to extrusion than a round section of the same size. Note that a square section is less suited to high-speed rotary service, where the larger contact area raises friction and heat.

Typical settings include automotive, general industrial maintenance, and construction equipment.

Order part number SH70353, sold individually. Nominal inside diameter is listed as 5 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.