replacement for the ultimaker feeder with lots of small changes-uses rollerblade bearing to press fibre against hobbed bolt -spring-loaded system -big handle to simplify filament change -herringbone-gear systemthis resolves all of the bugs I discovered (so far) while using the first version of my feeder.in addition to the standard ultimaker feeder pars you will also need: 1x rollerblade bearing, 2x springs, 2x long m3 screws & nuts.apart from the need to re-calibrate the feeder motor (the gear system used leads to an extrusion of ~95mm when I swap the stock ultimaker gearing with these) this works as a drop-in replacement for the feeder system.