Prusa i3 MK2.5S/MK3S/MK3S+ Extruder for Mosquito Hotend | Bondtech

  • Bondtech Prusa Upgrade
  • Prusa Mosquito Upgrade
  • Prusa Extruder upgrade


Bondtech Extruder for Mosquito Hotend

A lightweight high-resolution extruder upgrade for the popular Prusa i3 MK3S and MK2.5S 3D printers with optimized design to use Mosquito and Mosquito Magnum hotends.

Product Main Features
Adapted to fit Prusa’s new filament sensor and Mosquito hotends
Includes one Bondtech BMG extruder with 3:1 gearing ratio
Optimized geometry for heat-sink cooling
Less moving weight to reduce vibration and ghosting
Professional SLS 3D printed housing and 3 other key parts

Prusa MK2.5S
Prusa MK3S
Prusa MK3S+

Step by step guides: Click here 

(Please read the guides before ordering to make sure you are comfortable with the steps involved)

This kit contains only the necessary parts to convert your current extruder
This upgrade kit does not include the Bondtech drive gears (already supplied by Prusa)

To use this upgrade kit, you will also need to buy the following:
Mosquito Hotend or a Mosquito Magnum Hotend
Boron Nitride Paste
SLS X-Carriage Kit for higher temperature and mechanical resistance - the STL Files for the X-Carriage can be downloaded from the Bondtech server.
Click here to download the Front
Click here to download the Rear

Optional items:
12v 50w Heater Cartridge (for the MK2.5S version)
24v 50w Heater Cartridge (for the MK3S/+ version)
One or more Nozzles, if you want to print abrasive materials like carbon, glass fiber or metal filled materials we recommend a Micro Swiss M2 Nozzle
1.5Nm Torque Wrench to properly tighten the nozzle

Working temperature limits

Bear in mind that if you use this upgrade kit inside a closed chamber, it will have the following set of working temperature limits:
Due to the sensor plastic parts made of HT PLA > up to 60°C (90-100°C when parts are annealed)
Due to the stepper motor > up to 80°C.

MK3S/MK3S Mosquito, what’s the difference?

This Upgrade Kit is similar to the previous MK3S kit, with the main difference of having been designed to fit the Mosquito and Mosquito Magnum hotends.
Other differences include:
An optimization of the cooling air channel to focus the airflow on the Mosquito’s heatsink. The channel is narrower.
This tighter space is also used to hold the hotend in place during nozzle changes, so the user can change the nozzle with a single hand.
The fan shroud was also redesigned to fit the Mosquito hotends.
Include in this kit is a new part, the Mosquito hotend adapter, 3D printed with SLS.

Prusa’s Heater or Mosquito Heater, what should I use?

The Upgrade is compatible with the thermistor and 40w heater already supplied with the Prusa (MK3s).
A 30W heater (most mk2.5s users) will likely not be sufficient enough to keep the Mosquito Hotend at a stable temperature.
However, you have the option of using a Slice Engineering 50W heater.
We recommend the more efficient 50W heater for your Mosquito to reach a stable operating temperature faster.

  • If you have a Prusa i3 MK2.5S, buy the 12v Mosquito heater.
  • If you have a Prusa i3 MK3S, you should buy the 24v Mosquito heater.

We highly recommend using a thermal compound paste to provide good thermal conductivity between the heater and the hotend.
Slice Engineering recommends the use of Boron Nitride Paste.

Updating the Firmware

To use this upgrade in the MK2.5S / MK3S, the E-steps and Z Max needs to be updated. Check out the latest version of the Bondtech firmware here.
Bondtech also supplies firmware versions compatible with the Mosquito’s thermistor. If you are using this Mosquito’s component, you should use the related firmware.


To use the MMU2s together with the Bondtech an extra Add-On is required (download below) to allow the sensor to trigger once the filament reaches the drive gears.

Bondtech has the following sets available:

All credits to Leon Van Roosmalen for his amazing design. Find more information about his work and designs here:

Community involvement

This is a co-development work with awesome guys in the Prusa Community like Chris Warkocki, Grégorie Saunier (Bear Upgrades), Olof Ogland, Erik Bjorgan, Josh Jones, Kyle Wiehe, Marc Evertz, Matt Harrison, Ocie Ward, Sando Bendig, Vecko Kojchevski (Vecko Extruder), Steven Mölby, and Yuri Delia that have provided excellent feedback and suggestions of how to develop the “perfect” extruder setup for the Prusa series printer. A lot of work has been put in this project and we tried to listen to all the inputs in order to find a solution that can be the best fit to the Prusa I3 MK3S.

View AllClose

Additional Information

Extruder & Hotend Parts (Print Head)
Extruder & Hotend Parts (Print Head)
Brand Name:
View AllClose