Replaces most RP2100 *remote* thermostat circuit boards. Not to be confused with the main PCB found on the heater itself. Other RP2100 parts listed here: Raypak RP2100 Gas Heater Parts
These commonly fail when the protective overlay breaks down, allowing moisture in, corroding the circuit board.
These are discontinued from the manufacturer, and one stock is depleted, they will no longer be available.