Used to push into filament spools to give a 8mm hole so you can hang the spool on some 8mm threaded rodshould just push fit and be okay but does have 4 holes so you can use small self tapping screws if needed.Print in PLA to get a nice easy movement then use 2 x m8 nut and 2 x m8 Penny washers to keep it on the threaded rod. Use another m8 nut if you need to keep the main nut from moving and adjusting tension