Heater elements: #2-05-0025 / MFG#12 to 0100-k love Used in Spa Builder Systems: AP-1, AP-1400, EP-1, LX-15 and LX-35 REPLACEMENT OPTIONS: Love #sd6000-156 / MFG#6000 to 156. AI#2-00-0109 / MFG#b24055qc MFG#c2550-0456 MFG#c2550-0556 MFG#c2550-0056et