Original Prusa i3 MK3S/+ to MK3.5S upgrade kit
Supercharge your MK3S and MK3S+!
With the introduction of the MK4S, we were looking for ways to bring its features to our proven workhorse, and the MK3.5S upgrade is the answer. It’s the easiest and most affordable option to print two times faster and expand the capabilities of your MK3S/+ 3D printer!
Enjoy benefits such as super-fast printing with the addition of Input Shaper, sending files wirelessly to your machine without using Raspberry Pi, and navigating the printer’s menus faster than ever before with the new large LCD. The upgrade is straightforward to install and with our detailed assembly guide and 3D printing handbook, you’ll be up to speed in no time!
High-speed printing with ease
As a part of the upgrade package, you will receive our new 32-bit embedded xBuddy to expand your 3D printer’s capabilities. The addition of Input Shaper and Pressure Advance brings a massive boost to your MK3S/+, allowing you to print more than twice as fast and with the same level of quality. The prints that would be otherwise running the entire night can be finished in just a few hours.
Prusa Connect and easy networking
With the MK3.5S upgrade, you also receive an easy way to connect your printer to your network - both wired and wireless. Add the MK3.5S to Prusa Connect, our internally developed remote print management solution, and start sending print files to your printer without the need to deal with USB drives. G-code streaming enables you to start printing mere seconds after you upload the file to the Prusa Connect cloud. However, Prusa Connect can do even more. Check out our article to learn all about it!

Plenty of quality-of-life improvements
It’s time to replace the old segmented LCD with a brand new one. This 3.5’’ color LCD gives you much better control over your printer. See print file previews, read detailed instructions, or scan QR codes - using the printer is now much more convenient. With the new electronics and the new LCD, you can now use standard USB flash drives for storing G-codes, and you can also use a USB drive to flash new firmware (but you can also do it remotely via Prusa Connect). You can customize which information is displayed at all times in the footer of the LCD screen.
PSU & Heatbed info
Before you order the upgrade, please check which PSU your printer came with and which version of the heatbed connector is installed. This is important for correct compatibility with the upgrade. Depending on the selected options, we can send you additional components to ensure compatibility with the upgrade.

Which PSU does your printer have?
- Black PSU - you are all good
- Silver PSU - you will need to add a compatible wiring harness or a black PSU (in the configuration box above)

How many screws does your heatbed have?
- 2+3 screws (power cable connected with screws) - you are all good
- 2+1 screws (power cable soldered) - replacing the bed will be necessary
Package Includes
This product is supplied as a kit - you must assemble it yourself!
PETG printed parts are NOT included! Please print them before you disassemble your MK3S/+! The filament is included in the upgrade package.
Important: The black injection-molded spool holder is not part of the upgrade package. If your printer didn't come with it (early revisions of MK3), you can purchase it here.
This product includes:
- 32-bit xBuddy board (same as MK4S)
- Metal xBuddy case (and cover)
- xLCD screen + cables (same as MK4S)
- Cable adapters for your current extruder and heatbed
- Expansion joints for Heatbed
- Fasteners and other accessories
- Filament for printable parts
- WI-FI module
- NFC module
- Injection molded parts
Parts kept from your MK3S/MK3S+
- Extruder with V6 hotend
- Frame and extrusions (the new MK4S has just a different look)
- PSU* (same wattage/voltage as MK4S)
- Heatbed MK52 24V (thermistor and power cables will be changed)
- X/Y/Z/E motors
- X/Y/Z rods and bearings
MK3S/+ Upgrades Comparison
MK3.5S upgrade | MK3.9S upgrade | MK4S upgrade | |
High-Performance 360° Cooling | No | Yes | Yes |
High-Flow Nozzle | No | Yes | Yes |
Build volume | 250 x 210 x 210 mm | 9.84 x 8.3 x 8.3 in | 250 x 210 x 220 mm | 9.84 x 8.3 x 8.6 in | 250 x 210 x 220 mm | 9.84 x 8.3 x 8.6 in |
Mainboard | Custom 32-bit xBuddy electronics with STM32 | Custom 32-bit xBuddy electronics with STM32 | Custom 32-bit xBuddy electronics with STM32 |
Stepper Drivers | Trinamic 2130 | Trinamic 2130 | Trinamic 2130 |
Stepper motors | Regular 1.8° X,Y stepper motors | Regular 1.8° X,Y stepper motors | Precise 0.9° X,Y stepper motors (prevents VFA) |
MMU3 support | Yes | Yes | Yes |
Extruder electronics | No | Custom breakout board for connecting fans, thermistors and other parts. | Custom breakout board for connecting fans, thermistors and other parts. |
Filament path | Aluminum heatsink, all-metal hotend | Aluminum heatsink, all-metal hotend | Aluminum heatsink, all-metal hotend |
Drive system | Direct drive | Nextruder Planetary Gear System, 10:1 gearbox ratio | Nextruder Planetary Gear System, 10:1 gearbox ratio |
First layer calibration | Manual adjust Z | Fully automatic (thanks to the Load Cell sensor) | Fully automatic (thanks to the Load Cell sensor) |
Quick-Swap nozzle system | No | Yes | Yes |
LCD screen | 3.5″ graphic 65k color screen | 3.5″ graphic 65k color screen | 3.5″ graphic 65k color screen |
Bed calibration | Automatic, Mesh Bed Leveling | Automatic, Mesh Bed Leveling (only on print area) | Automatic, Mesh Bed Leveling (only on print area) |
One-click Printing | Yes | Yes | Yes |
Status LEDs | Yes | Yes | Yes |
Input shaper | Yes | Yes | Yes |
Filament Sensor | Yes (IR) | Yes (built-in Hall sensor) | Yes (built-in Hall sensor) |
Loadcell sensor | No | Yes | Yes |
Advanced sensors | 3 thermistors + SuperPINDA, fan RPM sensors | Filament sensor, Loadcell sensor, Power panic, 4 high-precision thermistors (genuine Semitec) + fan motors RPM monitoring | Filament sensor, Loadcell sensor, Power panic, 4 high-precision thermistors (genuine Semitec) + fan motors RPM monitoring |
Power panic | Yes | Yes | Yes |
Ethernet connection | Yes | Yes | Yes |
Wi-Fi connection | Yes | Yes | Yes |
NFC connection | Yes | Yes | Yes |
Prusa Link | Integrated | Integrated | Integrated |
Print medium | USB drive / LAN / internet via Prusa Connect | USB drive / LAN / internet via Prusa Connect | USB drive / LAN / internet via Prusa Connect |
Firmware update interface | USB drive | USB drive | USB drive |
Kit price | 249 USD / 279 EUR (VAT incl.) | 499 USD / 549 EUR (VAT incl.) | 579 USD / 639 EUR (VAT incl.) |
Buy MK3.5S upgrade | Buy MK3.9S upgrade | Buy MK4S upgrade |
The MK3.5S kit is the most cost-effective option to upgrade your MK3S/+ with plenty of new and useful features, including doubled printing speed thanks to Input Shaper and Pressure Advance support. You will get 32-bit electronics along with a new LCD, as well as Wi-Fi, LAN and NFC connectivity with support for remote print management via Prusa Connect. Nextruder is not included.
Before you order the upgrade, please consult the product description on which PSU your printer came with, which version of the heatbed connector is installed and about MMU3 compatibility.
This product is supplied as a kit - you must assemble it yourself. Injection molded parts are included, other PETG printed parts are not included. Please print them before you disassemble your MK3S/+! The necessary filament is included in the upgrade package.
Preparation time: 1-3 business days.