1. Suitable for both flat roof and slope roof 2. Employing sliding way for the frame, much easier for installation, especially suitable for European-styled houses 3. Still works as normal as before even one vacuum tube destroys 4. Hailstone resistance: 25mm 5. Higher efficient, stable performance, beautiful design 6. It can endure 0.6Mpa high pressure 7. It can be used for solar water heater or solar air condition