GB/T 1216-2004 "external micrometer" standard, a comprehensive specification of the outer diameter of the micrometer. Clarify its type, basic size and Measurement range. Strictly stipulate the manufacturing process, Accuracy grade and other mass requirements, through rigorous testing and inspection rules to control the quality. At the same time standardize product labeling, Encasement details. The standard provides unified guidelines for the production, mass detection and use of external micrometers to ensure that external micrometer measurement is accurate and reliable, to meet the needs of precision measurement in various industries.