Vacuum tube material: borosilicate glass Absorption of ive coating: ≥0.92 (AM1.5) Emission of ive coating: ≤0.065  Vacuum: <3 ?0-2 Pa Stagnation temperature: >200C Solar radiance exposure: ≤3.0MJ/m2 Max strenth:0.6Mpa The tube is made of extremely strong transparent borosilicate glass, but the inner tube is coated with a special ive coating, which features excellent solar heat absorption and minimal heat reflection properties. The air is evacuated the space between the two glass tubes to form a vacuum, which eliminates conductive and convective heat loss.