Ordinary people believe that a precision aluminum alloy cylinder has excellent quality, which is reflected in the selection of alloy materials. Professionals believe that the processing technology of aluminum alloy cylinder block is more important for good quality: the ovality tolerance can reach 0.02-0.05 mm. The straightness can reach 5 / 10000. In addition to the ultra-high precision and strict dimensional tolerance requirements, the surface treatment is also extremely harsh. Thickness of hard oxide film 40 μ~ sixty μ， The film hardness can reach above hv450. The insulation resistance of the film can exceed 1000K Ω. The breakdown voltage is greater than 450V. The surface gloss can reach Ra0.2 in mass production. Any one of these standards is higher than the European and American standards.