PLEASE READ BEFORE PURCHASE. Water Heater FVIR (Flammable Vapor Ignition Resistant) or FTR Fixed Thermal Release for FVIR or FV or TRD system (Flammable Vapor Ignition Retardation System). Product is compatible with FVIR type water heaters. Installation instructions may be found online or through the manufacturer of the water heater. The image is an example of the interchangeable part that you will receive. This product may have a different "AP" number associated then the one in your water heater. Please message seller directly with any questions or concerns prior to purchasing.