I needed a spool holder for 3kg spools. Rail Mount seemed like a good idea. It works with standard 1Kg spools.

The 3kg spool designed for is 12" diameter x 4" wide with a 32mm center hole.

The rack is a Home Depot heavy duty rack.

I used

(4) 5mm Brass inserts, using a soldering iron to heat press into the hole

(4) M5 x 12mm Button Head Cap Screw

I printed out of ABS for strength, 5 walls, 25% infill Gyroid.