wanted to make something out of all my empty spools so came up with this cat toy to glue to the inside of the spool they are small enough to fit into cages so i print these and give them to local animal shelters these were designed for the Numakers spools but they are a common size they will work in a lot of different brand spools Numakers spools are about 200mm wide and about 58.25mm inner diameter. I use 3d gloop to fix the track to the spool but you can use any kind of super glue cr glue you prefer for shorter spools there is a skinnier track in the raw files