XPR B-lip X-Pac U-Cup is a versatile reciprocating seal for linear rod applications, up to 400 bar. The rubber expander creates a compression style seal while still operating as a pressure actuated U-Cup design. The result is better low-pressure sealing and less startup leakage. The XPR X-Pac features a Twin-Lip design which offers increased seal stability and superior sealing ability. MFP Seals' X-Pac U-Cups feature a knife trimmed sealing lip for increased sealing ability.