This is the 2 ball bearing installed compatible level winder worm shaft of ABU 2500C, made by aluminum alloy to remove weight. Fits to 2500C, 2501C, 2600C, 2601C, 3500C. 3.0g (genuine worm shaft 6.1g) Ball bearings removes friction in roration drastically. Plastic part is made of Duracon POM to offer friction-less operation.