Sta-Rite SR400LP Max-E-Therm Pool And Spa Heater, Propane, 400,000 BTU Lightweight - Lightest heater in its class Compact Design - Ideal for retro-fit installation Lower operating costs - 84% efficiency rating - rated 1st in its class for highest energy efficiency Rustproof Housing Sleek, matte black enclosure is made of Dura-Glass - an exclusive Sta-Rite material that handles the heat and weathers the elements Custom or Retrofit - Direct-connects to Sta-Rite System:3 Mod Media filter or easily fits other systems