Bondtech MK3S / MK2.5S Mosquito upgrade

Bondtech MK3S / MK2.5S Mosquito upgrade

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  • Lightweight high-resolution extruder upgrade for the popular Prusa i3 MK3S and MK2.5S 3D printers
  • Optimized to use with Mosquito and Mosquito Magnum hotends.


Upgrade your Caribou, Bear or Prusa
Upgrade your Prusa with a Bondtech Mini Geared extruder featuring higher gear ratio – 3:1 – that allows for extra push force and higher resolution.

Print Faster Or With Higher Quality
This lightweight extruder will allow your 3D printer to print faster or to achieve even better surface quality.

Reduce 3D Printing Issues
Decrease the risk of heat creep to avoid clogs and improve filament feeding by avoiding slipping and deformation that cause under and over extrusion issues.

Upgrade kit With Optimized Design to fit Mosquito hotends
This is a Bondtech upgrade for the popular Prusa I3 MK3S and MK2.5S that will allow the use of the world acclaimed Mosquito hotends.

Bondtech Extruder For Prusa i3 MK2.5S & MK3S
This kit contains only the necessary parts to convert your current extruder to our own popular design based upon our BMG (Bondtech Mini Geared) extruder with 3:1 gearing ratio for better precision and resolution together with optimized geometry for the heatsink cooling and professional SLS 3D printed housing.

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

NOTICE: This Upgrade Kit does not include the Bondtech drive gears (already supplied by Prusa).

To use this Upgrade Kit, you will also need the following:

  • a Mosquito Hotend or a Mosquito Magnum Hotend for higher material flow
  • the Boron Nitride Paste
  • For Prusa you need the FDM X-Carriage Kit (you can download the STLs in the Resources section and 3D print them ) or the SLS X-Carriage Kit for higher temperature and mechanical resistance

Optional items:

  • the Mosquito HT Thermistor (for the MK3S version only, firmware update required)
  • a 1.5Nm Torque Wrench to properly tighten the nozzle.

Product Main Features
This extruder upgrade presents the following 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

MK3S / MK3S Mosquito, What’s the difference?
This Upgrade Kit is mostly similar to the previous MK3S, with the main difference of having been designed to fit the Mosquito and Mosquito Magnum hotends.

Other differences come from the design changes that 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
  • We include in this kit a new part, the Mosquito hotend adapter, 3D printed with SLS

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 our firmware.

To use the MMU2s together with the Bondtech an extra Add-On is required. This will allow sensor to trigger once the filament is reaching the drive gears.

You can download the STL file bundles from our MMU2S Add-On Files from Bondtech:

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.

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