ISO 19347:2015 specifies the principal characteristics of synchronous endless belts and pulleys for use in synchronous endless belt drives for mechanical power transmission and where positive indexing or synchronization is required.
The principal characteristics includes the following:
a) belt nominal tooth dimensions;
b) belt length and width dimensions and tolerances;
c) belt length-measurement specifications;
d) pulley grooves dimensions and tolerances;
e) pulley dimensions and tolerances;
f) pulley quality specification.
 These drives have been known under various names in the past, for example: timing belt drives, positive belt drives, gear belt drives.