BMG for Prusa MK3S to Fit Mosquito
BMG for Prusa MK3S to Fit Mosquito
BMG for i3 MK3S Mosquito Fit
BMG and Mosquito for Prusa
BMG for i3 MK3S Mosquito Fit
Prusa i3 MK3S+/MK3S / MK2.5S Mosquito® Parts
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Prusa i3 MK3S+/MK3S / MK2.5S Mosquito® IDGA

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

5 in Stock


Frequently bought with:

Product Main Features

This extruder upgrade kit is for the Prusa i3 MK2.5S / MK3S / MK3S+. Its main features include:

  • Compatibility with Prusa’s new filament sensor and Mosquito Hotends
  • Bondtech BMG extruder drive train with 3:1 gearing ratio
  • Optimized geometry for heat-sink cooling
  • Mount for PINDA probe
  • Less moving weight that reduces vibration and ghosting
  • Professional SLS 3D printed housing and 3 other key parts

Please note: This product does not include Bondtech drive gears. The Bondtech drive gears are included with your Prusa printer already.

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

Optional items:

Upgrade Your Prusa

Upgrade your Prusa with a Bondtech Mini Geared extruder featuring a high 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 achieve even better surface quality.

Reduce 3D Printing Issues

Decrease the risk of heat creep, 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

Directly integrates with Mosquito and Mosquito Magnum Hotends

Bondtech Extruder For Prusa i3 MK2.5S, MK3S, & MK3S+

This kit contains all of the necessary parts to convert your current extruder to Bondtech's popular design based upon the BMG (Bondtech Mini Geared) extruder with 3:1 gearing ratio. This extruder features high precision and resolution, optimized geometry for 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:

  • Up to 60°C (90-100°C when parts are annealed) due to the plastic parts made of HT PLA
  • Up to 80°C due to the stepper motor

MK3S / MK3S Mosquito, What is the Difference?

This upgrade kit is almost identical to the previous MK3S upgrade kit, except that is has been designed to be compatible with the Mosquito and Mosquito Magnum Hotends. Other differences come from the design changes that include:

  • Optimization of the cooling air channel to focus the airflow on the Mosquito’s heatsink. The channel is narrower.
  • Tighter space to hold the hotend in place during nozzle changes so the user can change the nozzle with a single hand
  • A redesigned fan shroud to fit the Mosquito Hotends
  • The Mosquito Hotend adapter which is 3D printed with SLS and included in this kit

Prusa’s Heater or the 50W Heater, What Should I Use?

This upgrade kit 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 also have the option of using our Thermistor and 50W Heaters (which are more efficient at reaching a stable operating temperature). Choose between our12V 50W Heater Cartridge (for the MK2.5S version) or the 24V 50W Heater Cartridge (for the MK3S version)

We highly recommend using our Boron Nitride Paste to provide good thermal conductivity between the heater and the hotend.

Updating the Firmware

To use this upgrade in the MK2.5S / MK3S with the Mosquito Hotend, the E-steps and Z_Max need to be updated. Check out the latest version of the firmware here


To use the MMU2s together with this upgrade kit, an extra add-on is required. This will allow the sensor to trigger once the filament is reaching the drive gears. You can download the STL file bundles below under the MMU2S Add-On Files Section. 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. 

Step By Step Guides

00. Bondtech Prusa i3 – Firmware Update

01. Prusa i3 MK2.5S / MK3S Upgrade Kit – Strip Reusable Parts

02. Prusa i3 MK2.5S / MK3S – Mosquito Upgrade Kit – Installation

Technical Specification

  • Article number: EXT-KIT-69
  • EAN code : 7350011410675
  • Net weight : 378g
  • Gross weight : 389g
  • Package Size : 137x94x65 mm
  • Gearing ratio : 3:1
  • E-steps value : 415 @16 bit micro-stepping; or 830 @32 bit micro-stepping
  • Extruder Housing : SLS Printed parts in Polyamide 12

Stepper Motor

  • Lightweight 25 mm pancake stepper with 18 N/m torque.
  • Max Input Current : 0.8A
  • Max chamber working temperature : 80℃

X-Carriage: Requires buying or 3D printing (see below) new X-Carriage R2 Front and Rear
Firmware: Bondtech adapted version required.

Licensing: This Project is licensed under GPL V3.0 and the STEP files are available for download.


Bondtech Github contains the STEP file, installation manual, exploded view, and more.

The 3D printed parts of this kit can be downloaded below as STLs:


Find and download the firmware here.

Find a guide on how to install the firmware here.

MMU2S Add-On files

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