Bondtech LGX for MK3S & Mosquito


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This is a LGX upgrade kit to use on Prusa MK3S and MK3S+ with only Mosquito or Mosquito Magnum hotends from Slice Engineering.

A compatible X-carriage and Mosquito hotend are required.

Requires a X-carriage - Bondtech LGX X-carriage for MK3S & Mosquito
You may download the x-carriage model, change it and/or print it yourself.

Product Includes:

  • LGX® Large Gears eXtruder
  • LGX Accessories for MK3S & Mosquito

Direct Drive Upgrade
This LGX™ based upgrade kit is an easy to install replacement of the stock direct drive extruder. It requires the accessories included in the LGX™ Accessories for MK3S & Mosquito package.

Easy To Install
Very intuitive and easy to install upgrade kit where the extruder faces the X-carriage reducing the distance between the nozzle and the x-axis.

Leading Grip Power
The LGX™ is the Bondtech extruder with the highest filament grip due to its new large drive wheels that put more teeth engaging the filament.

MMU Compatibility
This upgrade kit is not compatible with any MMU version.

Community Sourced Design

This extruder design is based on Gerd Jentz‘s project posted on GitHub. To check the project and its geometry files click here. To his project Bondtech made some small adjustments and added their own filament sensor housing and X-carriage design, compatible with the stock MK3S X-axis.

Custom Firmware Required

You need to update your Prusa’s firmware to use this product.

New Firmware Available.
Open the Firmware tab on the Bondtech site to download.

Enjoy Bondtech’s Evolved Dual Drive Technology
Start using our newest extruder with our new Dual Drive Technology based on larger drive gears. This is only one of the 7 new features Bondtech implemented on an extruder.

7 new features on a Bondtech eXtruder:

  • Larger drive wheels, for increased filament grip;
  • Filament pre-tension lever, for repeated results;
  • Multi-function interface socket, for tool or application quick swap;
  • Drive wheels’ maintenance windows, for easy cleaning;
  • Compact, light & symmetric design, for increased performance and compatibility;
  • Multiple mounting hole patterns, for easy and flexible setup;
  • A small step for a greener Future, craft boxes without bleaching & no coating.

3D Printed Housing using PA12

The housing parts are professionally printed with nylon for maximum strength and precision and higher temperature resistance.

Working Temperature Limits
Bear in mind the working temperature limit of this upgrade kit will have the following set of limits:

  • Due to the stepper motor > up to 70°C.
  • The PA12 parts themselves can withstand up to 100°C.

Technical Specification


  • e-steps value : 400 using 16 microsteps;
  • Drive wheels : hardened steel;
  • retraction speed : 35 mm/s
  • retraction distance (direct drive) for rigid materials : 0.4 mm
  • retraction distance (direct drive) for soft materials : 3 mm
  • Max operating temperature : 70°C
  • Max tightening torque on the extruder screws is 0.3 Nm
  • Max tightening torque on the heatsink/cold block screw is 0.6 Nm
  • LGX™ DD net weight : 218.6 g
  • Package measurements : 80x103x73 mm
  • Package weight : 269 g


  • Requires cable with PHR-6 connector
  • 2 phases
  • DC 3.1 V
  • Max 0.7A / phase

To use the LGX, run the stepper motor with currents between ~0.45 and ~0.65A:

Be vigilant regarding the stepper motor surface temperature.
Keep it cool enough to touch. Lower Vref otherwise.

Class H motor, rated up to 180°C

  • Max recommended environment : 70°C
  • Max temperature at this environment temperature can go up to 130°C on account of the self heating.
  • Download the stepper motor Technical Data Sheet here.

Buy a Bondtech LGX for MK3S & Mosquito from Spool3D for your 3D printer in Canada without the surprise cost of the exchange rate!

Manufacturer Part Number: EXT-KIT-84


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