Hayward SPX0504Z7 R-40 Medium Base Bulb Replacement for Hayward Underwater Lights, 500-Watt R40 medium base bulb replacement Fits hayward underwater lights models sp0540, sp0541, sp0542, sp0543, sp0503 (400w, 120v), sp0504 (500w, 110v) 500 watt, 12-volt Weighs 3-Pound