This extruder upgrade are for Prusa MK2.5 or Prusa MK3 where you already have the Bondtech Drivegears. This kit contains the necessary parts to convert to our newly designed extruder with 3:1 gearing ratio for better precision and resolution together with optimized geometry for the heatsink cooling and many other cool features. It also lowers the moving weight to reduce ghosting and vibrations.