On metric drawings, the length of pitch diameter per tooth measured in millimeters is module.

Pitch Diameter

The diameter of an imaginary cylindrical surface that runs through the thread of a screw or gear, where this surface would make equal divisions between the peaks and valleys of the threads.

Metric Drawings

Technical drawings that use the metric system for dimensions, measurements, and scales, standard in countries outside of the United States.

Module

In engineering, a measure of gear tooth size which is the ratio of the pitch diameter to the number of teeth, influencing the gear's size and interaction.