Bondtech Upgrade Kit For Prusa i3 MK2.5 & MK3





Upgrade Kits


Prusa I3 MK2.5-MK3 Extruder upgrade

EAN13: 7350011410941 SKU: EXT-KIT-63 Categories: , , , Brand:

Prusa I3 MK2.5-MK3 Extruder upgrade

(1 customer review)

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.



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With the new Add-On this kit supports MK3s filament sensor.

Download the files for the printable Add-On here:

This extruder upgrade kit is for the Prusa MK2.5 or the Prusa MK3 where you already have our Bondtech gears. This kit contains the necessary parts to convert to our freshly designed extruder that uses 3:1 gearing ratio for improved precision and resolution, optimized geometry for the heat-sink cooling and many other improved features.
It also reduces the moving weight to reduce vibrations and ghosting.

This is a co-development work with awsome 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 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 spent in this project and we have tried to listen to all the inputs in order to find a solution that can be fitted to a Prusa I3 MK2, MK2S, MK2.5 and MK3.

The extruder parts are not optimized for FDM printing but for SLS printing that we use to produce the housing parts in polyamide 12 for maximum precision and strength.

This kit comes with this 25 mm pancake stepper that have 18 Ncm in torque for a lightweight but powerful extrusion and a new stepper cable for connecting the motor.

The original part-cooling fan 50×15 radial fan is used in this setup and is not included.

The original 40x40x10 heat-sink cooling fan is used in this setup and is not included.
For more effective HotEnd cooling we recommend a fan with high pressure like Sunon’s MF40100V1-1000U-G99 or similar.

The original filament sensor cover is used and is not included.

This extruder will fit the stock  MK2.5 / MK3 carriage’s and also other popular designs like Vecko, Zaribo and Bear. Check the guide for available X-Carriage here:

The E-steps needs to be updated to 415 for MK2, MK2s and MK2.5 and is easy to do by downloading this g-code file, put it on the SD card and select to print the file esteps.gcode which will set the esteps and save it. For MK3 it needs to be 830 as it uses 32 bit microstepping, use this file instead.

Weight reduction is 121 g, from 387 g as default setup compared to 266 g for this setup (Extruder, motor)

This project is licenced under GPL V3 and the STEP-files are available for download here:


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 bundle here: MMU2s Add-On for Bondtech MK2.5/MK3.
All credits to Leon Van Roosmalen for his amazing design. Find more information about his work and designs here:

Freight Weight 392 g
Dimensions 15.5 × 11.5 × 10.5 cm


Bondtech Github. Contains Stepfile, installation manual, exploded view, and others.

Latest Firmware

Based on 3.13.3 Firmware for MK3, MK3S, MK3S+, MK2.5 and MK2.5S

The firmware archives you will find below are based on the Prusa release mentioned above. All updates were done by Bondtech to optimize the usage of our BMG based hardware and sometimes to tweak specific features. You may find more information on the release notes below.

MMU2S & MMU3 Support

This firmware release supports Bondtech customers that are using the MMU2S or MMU3 with Prusa i3 MK25s or MK3s, and E3D or Mosquito hotends. Expand the tab that fits your 3D printer and choose the firmware file most adjusted to your configuration.

About this release

Please read Prusa’s release note to know about all changes : 3.13.3 Firmware

Source Code

Click the link below to visit the Source Code page to clone or download.

Select the Bondtech MK3 FW3133 branch

The HT firmware versions should only be used with Slice's 450C thermistors.
For Slice's 300C thermistor, choose the non HT version.

Do not use any of the files below with LGX based Upgrade Kits.
For LGX based upgrade kits look for firmware on the related Product Page.

For RAMBo 10a Mainboards

For RAMBo 13a Mainboards

For RAMBo 10a Mainboards

For RAMBo 13a Mainboards

For RAMBo 10a Mainboards

For RAMBo 13a Mainboards

For RAMBo 10a Mainboards

For RAMBo 13a Mainboards

For older versions Click here

To learn how to install a firmware update on your Prusa i3

Click here

1 review for Prusa I3 MK2.5-MK3 Extruder upgrade

  1. Vicente Gomez (verified owner)

    By far the best upgrade I’ve done to my stock MK3, hands down. I was having issues with inconsistent prints and my extruder producing to much heat which would cause the filament to melt and blob up stopping my prints. Once upgraded I could immediately notice the print quality was 10 times better and the new pancake extruder wasn’t anywhere near as hot as my stock extruder. Best upgrade ever.

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