Features of Boilers:- Outer shell made of pre-painted gray steel (RAL 9006)- Made of 3 mm thick DCP steel, baked at 850 ° C - Double coated glass with titanium for longer life.- Strong polyurethane insulation with a density of 50 kg / m³ and a thickness of 70 mm (to retain hot water)- 4 kW electrica..