This International Standard specifies the principal characteristics of synchronous pulleys for use in synchronous endless belt drives for mechanical power transmission and where positive indexing or synchronization is required. NOTE These drives have been known under various names in the past, for example: timing belt drives, positive belt drives, gear belt drives. The principal characteristics include: a) tooth dimensions and tolerances; b) pulley dimensions and tolerances; c) quality specification. As far as dimensions are concerned, the pulleys specified in this International Standard are used interchangeably with the belts specified in ISO 5296.