ISO 19347:2015

ISO 19347:2015 specifies the principal characteristics of synchronous endless belts and pulleys for use in synchronous endless belt drives[1] 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.

[1] These drives have been known under various names in the past, for example: timing belt drives, positive belt drives, gear belt drives.