It is designed to fit 3DPrintingNerd's bracket (12.5 mm thick). Heavy duty and a tiny bit overengineered , can hold up to 4 spools, to print just download the printable.stl file, I would suggest a small nozzle size on the parts that have threads. (In case you want to edit something from the f3d files make sure to set the threads to modeled or they will be removed !)

If you have trouble assembling this crazy contraption take a look inside fusion on the holder.f3d or message me ! (The holder.f3d file is not printable just the contraption put together in fusion360 to give a visual presentation, if you want to make your own stl from it SET THE THREADS TO MODELED!!!!!! not cosmetic, otherwise they WILL DISAPEAR!)