This is for the 1kg masterspool. For a 0.75kg design, see my other design here. The masterspool design leaves too much room between the filament and the sides of the spool. I think this is so that the zip ties fit, but it causes the filament to get caught and prints to fail. I recommend installing the spacer and loading filament onto the spool as usual. Remove the ties then fully tighten both halves together.