Belts for machines, namely, driving belts, transmission belts, [ V-belts, ribbed V-belts, variable speed gear belts, ] synchronous belts, [ studded belts, twin-tooth synchronous drive belts, flat belts, conveying belts ] * all aforesaid goods exclusively used for doors and door-opening systems and not for lifts, cranes, moving staircases and other conveyors for persons and loads, as far as these do not concern door and door-opening systems *