The symmetrical U-cup seals equally well on both rod and piston applications and eliminates the need to select either a specialized rod or piston design. The U-cups are compression molded of liquid cast polyurethanes to eliminate the quality problems frequently encountered in injection molded U-cups and to provide higher operating temperature limits. The Loaded Center U-cup produces the best all purpose seal for use in standard hydraulic fluids. Two Styles: CP - Open Center PP - Loaded Center Interchanges with Most Poly-U-Cups.  95 Durometer Liquid Cast Polyurethane.