Its a new filament driver for your thing o matic, the ony extra part you need is a spring. i took one from an old shimano derailleur, but its quite too strong and just blocks everything.... the ball bearing is an original one from makerbot. if you print it, tell me if your version works and if there are any tricks and upgrades to do. i have to wait for new plastic, since my delivery from 3d printerstuff is totally crap material.... :-)