Tolerance-balancing M12 Housing Screw Connections Phoenix Contact Tolerance-balancing M12 housing for THR contact carriers compensates process-related production tolerances for two-piece device ports. Phoenix Contact Tolerance-balancing M12 housing is a unique, floating snap-together assembly, installed in the enclosure, providing the compensation preventing force being applied to the solder joints. Optional colored shell sleeves are also available for color coding port connections.