 Conversely, in an internal (female) thread (e.g., in a nut), the major and minor diameters are "minimum" dimensions; therefore the thread profile must end flat at "D"min but may be rounded out beyond "D"maj.The minor diameter "D"min and effective pitch diameter "D"p are derived from the major diameter and pitch as

A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter "D" (the maximum thread diameter) and the pitch "P", both expressed in millimetres and separated by the hyphen sign, "-" (e.g., M8-1.25).If the pitch is the normally used "coarse" pitch listed in ISO 261 or ISO 262, it can be omitted (e.g., M8).