This filament spool is designed as an attachment for stock Ender 3 spool, but it will fit on any spool with diameter of 30mm where the 30mm part is at least 89mm wide. It can hold any spool with inner diameter of 53mm or more and width of 76mm or less. This spool reduces tensile load on a string which is important for printing flexible materials such as TPU. I made a youtube video on how to assamble it. It utilizes two 3d printed angular contact ball bearings.To assamble it you will need:Non-printed parts: 22 of a 6mm balls. You could get a metal ones, but it's just fine to use airsoft balls just like I do.Printed parts: spool1, spool2, two times cage, two times ring1 and two times ring2Materials:cage was designed to be printed out of ABS. Materials like PLA or PETG are too brittle for this application and probably won't work. Materials like ASA or Nylon might work.All other pars are designed to be printed out of PLA. Materials like ABS or ASA warp too much and probably won't work. Materials like PETG or PLAplus might work.Slicer settings:I printed with layer height of a 0,2mm and extrusion width of 0,45mm, but these settings are not required and only serves as an example.