MFP Seals XPAR B Lip X-Pac U-Cup is a versatile reciprocating seal for linear rod applications, up to 400 bar (5800 psi). The rubber expander creates a compression style seal while still operating as a pressure actuated U-Cup design. The result is a better low-pressure sealing and startup leakage. The XPAR X-Pac has an Anti-Extrusion Ring to prevent seal extrusion. MFP Seals X-Pac U-Cups feature a knife trimmed sealing lip for increased sealability.