Duda Solar 15 Tube Water Heater Collector 45&deg; Frame Evacuated Vacuum Tubes SRCC Certified Hot Hailstone Resistance: up to &phi;mm (1"), Max Operating Pressure: 87psi, Max Flow Rate: 5.25 gpm 14mm TU1 Copper Heat Pipes, Manifold insulation: 45mm 93 Kg/m^3 Rockwool, Rated Best Heat Retention &phi;58mm x 1800mm Three-Target Cu/SS-ALN(H)/SS-ALN(L)/ALN Vacuum Tubes, High Boron Silicon 3.3 Glass Sun Absorption Efficiency: 93-96%, Vacuum Rating: Less than 5.0 x 10^3 Pa, Lifespan:70% @ 15 Years OG-100 SRCC Certificate Number: 10001877, Eligible for 30% Federal Tax Rebate, Winter Resistant