Check if you got all the components of the MOD-KIT

[Your MOD-KIT version might be a newer version but the instructions are still almost the same] 


Shell, Clips, Switches, HOT-SWAP, Instructions, Screwdriver, Skates, Charging cable, Magnetic adapter, Battery, Replacement battery cable.
Screw Types
From left to right: Bottom screws, side button screw, mid screws, switch screws [Save those for the end]
[1] Add on/off switch
Pay attention to the orientation!
[2] Add the main PCB
Move the on/off switch to make it lock in.
[3] Check the scrollwheel spring
It has to sit in it's pockets.
[4] Fasten the PCB
Use 5 mid-screws.
[5] Add the side buttons PCB
Place the cable in front of the PCB.
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[6] Add the side button screw
Pay attention to the orientation!
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[7] Add screws to the clips
Use mid sized screws.
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[8] Add the clips
The clips are supposed to "sandwich" the main PCB.
[9] Add the switches to the HOT-SWAP
Pay attention to the orientation!
[10] Add the HOT-SWAP
Pay attention to the orientation of the cable. Use mid-sized screws.
[11] Add mid sized screws [Old MOD-KIT version]
These are for the post-travel calibration of the side buttons.
[12] Add mid sized screws
These are for the post-travel calibration of left and right click.
 If you have a P-SL SQ, MQ or LQ , P-GP LQ button cell MOD-KIT please continue following instructions here.
[13] Add the battery cable
[14] Add the battery
The micro USB socket should be in the back of the mouse.
[15] Add the adapter to the cable
[16] Push the magnetic adapter in the battery. Push against the battery from the other side.
You have to push more than you think. Check if it's charging [Battery LED is blinking green]
[17] Plug in the battery cable
The small pin should tell you the orientation. It looks like it's not all the way in - it is though!
[18] Combine bottom and top shell
Start with the side buttons going in front of the screws. Add the 4 bottom screws at the sides.
[19] Add the switch screws
Depening on the model there will be 2-4 holes.
[20] Add the skates
We recommend adding the small circle in the back.
[21] Caibrate the side buttons
By extending the screws behind the sidebuttons, you can reduce the post-travel.
[22] Check the mouse buttons
If the mouse buttons touch the shell in the front before they activate, you need to calibrate them.
[23] Calibration
To fix the mentioned issue, extend the screws in the mouse buttons half a turn to the left and check again.
[24] Pre-travel calibration
To calibrate the pre-travel, turn the screws in the clips to the left and pull down the mouse buttons.
[25] Install drivers
To change the DPI install drivers. Download Link to Onboard Memory Managment from the official Logitech Support site. Make sure to set the report rate to 1000. If you encounter issues with this software, try this one instead.