Sterling Seal & Supply Buna NBR X profile, Quad O-Rings do NOT tend to Roll in the groove during reciprocating movement X Profile seals were designed to overcome the weaknesses of O-Rings such as high friction, spiral failures and leakage from compression set The grooves on the inside and outside diameter of these Rings retain lubricant thereby lowering friction and extending seal life Lower Breakaway force and reduced operating pressures make Sterling Seal & Supply Buna NBR Quad O-Rings ideal in reciprocating applications 1-5/16ID nominal x 3/32CS nominal