solar heater1.15 years lifetime 2.high efficieny , resist hail and strong wind 3.Food material SUS304/2B 4.Low price Vacuum tube: Cercis SolarVacuum tube specification: Φ47×1.5m, Φ58×1.8m, Φ70×2.0mSteelInner tank: SUS304-2B for food grade stainless steelOuter tank: Stainless steel or galvanized steelHeat preservation: 50-70mm polyurethane wholly machinery compression form foamFrame: zinc plated ...