Pentair 42002-0024S Stack Flue Sensor Replacement Pool and Spa Heater Electrical Systems Stack flue sensor replacement Fits Pentair MasterTemp pool and spa heater electrical systems Also fits Pentair Sta-Rite Max-E-Therm pool and spa heater electrical systems model SR200, SR333, SR400 Measures 6-inch length by 6-inch height by 6-inch width