This simple part allows you to safely mount 1 kg spools, from every filament manufacturer, I've encountered. It really is handy! -Ryan
DOWNLOAD FILE 31.31 mm I.D. Inner Diameter
DOWNLOAD FILE 33.48 mm I.D. Inner Diameter (Updated 6-25-2017)
Some of the latest printers shipped, have an thicker shaft to hold the spools. The model has been revised to account for the design change.
This is a link for a digital file. This is not a physical product.