This is a 200x200 mm frame with x8 attachment points for the MMT (Modular Marker Tower) system.

The inner area is 180x180 mm where you can place the object to be scanned.
The outer size is 220x220 mm.

There are 16 holes on top where one can put D6x3 magnets to attach regular marker blocks if needed (see photos for examples). 
Or you could just place new markers on the walls in random order to make sure it does not confuse the tracking.
There are 24 holes at the bottom where you can put D6x3 magnets if you want, this allows the frame to be attached securely to a ferrous surface.
You can also place the regular bases for the MMT system underneath, or elevate the whole frame higher with the help of the spacers.

By connecting the towers with this frame, the rigidity is greatly increased.

Choice of filament material for the MMT:
This part was designed for use with Bambu Lab PLA Basic, but can work with other regular PLA of similar quality.
Matte PLA or Silk PLA should not be used due to their weaker mechanical properties compared to regular PLA.
 

Choice of filament color for the MMT:
Gray: Works well when scanning most objects in marker mode, and it will also work to assist tracking in geometry mode.
Black: Works well when scanning black parts, as it can otherwise risk overexposing the marker block, leading to loss of tracking.

The 3mf file has 1 pcs ready on the plate to be printed.

Added an introduction video for the MMT-system that you can find here: