This unification establishes the lengths of the flat ring transmission belts and the related tolerances. The lengths indicated below are internal lengths under a reference load which corresponds to approximately 1/10 of the breaking load of the belt. According to the nature of the belt and the manufacturing conditions, the manufacturer will give the belt the appropriate length when at rest.
UNI 4924-1962 history
1962UNI 4924-1962 Circular conveyor belt. Length and deviation