Pentair 460352 MiniMax 100 BTU Natural Gas Milivolt High Performance Pool and Spa Heater 100 BTU natural gas millivolt high performance pool and spa heater Millivolt standing pilot versions in natural gas Quiet and dependable operation from packaged burner system Bronze headers; installs to 3500-feet altitude Quick flange allow 1-1/2 FIP connect; measures 22-inch length by 28-inch height by 19-inch width