SummaryI have tried every filament clip I could find and there are some good ones but none fit all my criteria. Some of the common problems I ran into were: Too long to fit on full spool Not tight enough Easily dislodged when spools stacked next to each other I designed these to address those issues and so far they have been working very well. There is a 4mm wide version for MakerBot spools and a 5mm wide for other misc spools. Both are for 1.75mm filament. InstructionsI would recommend using a raft and going slow since these are small. I use one shell and a high fill, at least 30 - 50%. Getting the hole the exact right size is difficult, so you may need to drill it out.