Using a Logitech M185 innards, you can recreate your misspent youth with a new Logitech 3-button C7.

PARTS:
Logitech M185 (donor mouse)
M3 x 8 countersunk screws (six)

PRINTING;
Buttons - To get the best finish I printed the buttons and lid vertically, with the 3 buttons upwards with a brim and tree supports
Lid - Print vertically with the button holes, with tree supports but no brim.
Base - Prints flat with the bottom on the bed and with supports.

In my example print I've use PETG. The buttons need a bit of flex to the plastic to work correctly although PLA may be ok. My example images use SUNLU PETG in Bone White and Grey

DISASSEMBLE THE M185:
Undo one screw of the M185 to disassemble it entirely. You need the PCB with battery terminals, so carefully unclip this. You won't be using the wheel on your retro computer, so lift this out and fold the wheel sensor flat out of the way. The metal support can be flexed and removed from the PCB entirely. The retro middle button will press onto the wheel's "click" sensor, so leave this intact.

ASSEMBLY:
The PCB fits into the new printed base, so carefully feed the wires into the matching slots around the battery housing. The battery has to be at a slightly different angle to the M185 but the wires only need to be pushed into position. The positive wire (at the back of the mouse) pushes sideways into a slot. The negative spring end pushes down into a slot.

The PCB should be pressed down and slides towards the back of the mouse slightly into the clip at the front. Use a screw near the back of the PCB to hold this down, as accurate button action need the PCB secure. The design is for the PCB angled to sit lower at the front than back, so this is normal!

The buttons can be screwed tight to the lid of the mouse. It might hold intact without a screw or you can glue it, but a screw is fine.

The lid now sits on the base and attaches with 4 screws from underneath. Make sure you can press each button and hear a faint click. The middle button is louder normally.

Place a AA battery into the socket underneath and slide the new battery cover into place. It only fits one way. There is a USB dongle housing inside there if needed. I haven't managed to get the power button located accurately, so I've left the PCB switch visible from underside with the battery cover removed and it can be operated with a fine tipped pencil or the corner of the battery cover plate.

If you add slidy feet to your mouse, there's indented rings near all four corners to help locate them.

11 Mar 2026 - v54
- Improved the battery cover
- Seated the PCB better for improved button action
- Moved the structures in the lid for a better finish