30x21'' Flange: High-strength aluminum alloy materials, and use low centrifugation forging and heat-treated, so has the best rigidity and durability. Welding: A metal inert gas welding robot automatic method of high-precision welding. Due to the dynamic balance function even if the high-speed rotation, but also with the weaving machine to maintain good compatibility. After hard coating machine processing, to completely prevent corrosion and surface scratches. Even if the use of a few years, will maintain its durability and precision. Warranty period of two year.