Here in the states Ultimachine sells the couplers and 8 mm steel rods. The steel rods were part of a 5 rod kit to make a 3d printer. All these parts worked well in the assembly to get rid of the short belts. Only needed to cut one of the steel rods. A dremel with a metal cutting disk did the job without any trouble. Thanks for the information to make the upgrade Calum! By the way Ultimachine sells 3mm plastic. So far it is the best I have used that ships within the states.