This is a Gridfinity compatible storage box for spools and bobbins with a max. diameter of about 21mm.
My girlfriend uses these spool & bobbin holders by LEN polygon to store matching colours together. Each peg - we use the compact version - fits nicely into one compartment.
I started with a slightly more sophisticated design, and changed it to simple cylindrical compartments. Please choose your preferred design from the files.
The sizes are the ones, that we needed - just ask me, if you need other dimensions.