Was tired of bending my filament through those little holes on the spools, so made these clips so I could keep the filament secure, without bending it all crazy. Have 2.5, 3.5 and 4.5mm gap versions. I find 2.5 works good on plastic spools, 3.5 on carboard spools, and I included a 4.5 just in case. If you need a different size, let me know and I can make one real quick.