EXCELLENT QUALITY AND RELIABILTY QUICK-DISCONNECT BRANCH UNIONS, AVAILABLE IN METRIC AND INCH SIZES, EXCELLENT FOR ENCLOSURE THRU-WALL INSTALLATIONS, DIMENSIONS LISTED ARE THE TUBE OUTSIDE DIAMETER(O.D.) EXAMPLE: PBU1/4 (PNEMATIC BULKHEAD UNION 1/4" TUBBING) MAXIMUM WORKING PRESSURE 150PSI, MAXIMUM WORKING TEMPERATURE 140F