It is high pressure solar water tank with one or two cooper coil 1) One or two Cooper Coil built-in 2)Inner tank 1.2mm Thinkness SUS304 2B Stainless Steel, Outer tank 0.6mm Color Steel 3)Accessories: P/T Valve, Mg Rod, Electric Heater, Drain Valves4) The tank capacity from 100L to 500L5) The warranty within 5 years