I haven't determined exactly how small I can make things yet but this is getting close. Using a .07mm (.003") nozzle and .05mm layer eight shooting ABS/Carbon filament. The extruder is doing a remarkably good job of metering at these low flows but that will ultimately be the limiting factor for size. Need to come up with a different design and/or smaller filament. Impeller is about as good as its going to get. The connecting rod and sprocket need some more fiddling to get 100% infill.