Pressure Solar Water Heater, Solar Collector, Solar Working Station, Renewable Energy KEH58 Vacuum tube: 58x1800mm Inner tank: Stainless Steel 304 2B food grade Outer tank: Stainless Steel Outer tank dia.460mm Frame: Stainless Steel Insulation: 50mm polyurethane total forming with pressure and best density 40kgs/m3 Available sizes: 18, 20, 22, 24, 28, 30, 36 tubes with capacity 135L up to 325L