Applies to external micrometers reading to 0.01 mm, or 0.002 mm, having either fixed or interchangeable anvils with measuring capacities up to 500 mm. It specifies materials and properties, design requirements and general dimensions, accuracy requirements and also requirements for the respective setting gauges for larger micrometers. Appendix A provides notes on methods of test for external micrometers, and Appendix B deals with the recommended use of micrometers and their limitations as measuring instruments. Notes on the deviation on reading at any point in the measuring range are given in Appendix C.