Features: 1) Split water heater use tube solar collectors and the tube should with the copper heat pipe 2) The inner cover coating is aluminum fins 3) The heat conducts to the heat transfer liquid (anti-freezing liquid or water) via a copper pipe 4) Outer tank: SUS304 stainless steel 5) Inner tank: stainless steel 6) Insulation: foam 7) Support frame: stainless steel