ISO 17396:2017 specifies the principal characteristics of synchronous endless and open belts and pulleys of the profile systems T and AT for use in synchronous belt drives for mechanical power transmission and where positive indexing or synchronization can be required.

NOTE Synchronous belt drives have been known by various titles in the past: for example, timing belt drives, positive belt drives, gear belt drives.

The principal belt and pulley characteristics include

a) nominal belt tooth dimensions,

b) belt tooth pitch spacing,

c) belt length and width dimensions,

d) belt length measurement specifications,

e) pulley groove dimensions and tolerances,

f) pulley diameter and width dimensions and tolerances, and

g) pulley quality specification.

The belts of the profile systems T and AT are made of polyurethane with high-tension fine steel cord tension members in most cases. As far as certain forces are given in this document, these values are only valid for these kinds of belt. For polyurethane belts with different tensile cords, i.e. aramid or rubber belts reinforced with glass fibre, the values can be different. It is intended that the user and the manufacturer agree about suitable values. Open belts made of thermoplastic polyurethane can be spliced to work as endless belts in conveyor applications. In this case, the tolerances are not valid for the splicing area of the endless spliced belt.