Replacement 27", 120V AC, 770 Watt heater cartridge for all USI ARL and CSL/Classroom 27" roll laminators except machines with the following serial number sequences: 0****-****, 1****-****, 4****-****, 5****-****, 9****-****, G****-****, or W****-****. Note: when installing 770 Watt heater in a machine originally equipped with 1200 Watt heaters, for proper machine performance, both heaters must be replaced. May be listed as part number 517P or A9703 in Owner's Manual.