568-387 BUNA 70 SQUARE CUT RINGS

SH70387 is an AS568-387 black Buna-N (Nitrile) 70 Shore A Square-Cut Ring with an inside diameter of 17.955 in (456.06 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 18.375 in (466.73 mm). In service, this square-cut ring resists the spiral failure that affects round rings on long reciprocating strokes.

Expect good resistance to water, hydraulic fluids, and greases and lubricants. Buna-N (Nitrile) is valued for low compression set under sustained load and the most widely specified general-purpose sealing elastomer. Published continuous service range is -40°F (-40°C) to 250°F (121.1°C). Applications involving ketones or strong acids call for a different compound. The profile itself contributes simple lathe-cut manufacture at low tooling cost and a flat contact band that spreads sealing load across a wider area. Note that a square section is less suited to high-speed rotary service, where the larger contact area raises friction and heat.

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

This item is sold individually under part number SH70387. Nominal inside diameter is listed as 18 inch. Review your operating media and conditions against this specification before installation. 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.