This is a mix of the very nice clip done by Madox; the filament hole was too snug and we wanted the filament to travel freely - allowing us to mount the clip anywhere on the spool. We redid the filament hole to be 4mm and have nice thick walls to ensure a strong, flexible piece. Using a clip has made a night and day difference between tangled spools or not - we change filament spools a lot, so for us was a must.