Fits tightly into Hatchbox spindle to hold and spin around 8mm rod. I made it with how my Rigidbot prints its so dimensions aren't exact like expected. For example, the diameter of the hole is actually 8.26mm wide and the dimension of the outside that fits into spindle is 32.6mm. Confirm it works for me, printed 2 out fits snugly into spindle so they can't fall out (was annoying from other prints).2mm thickness, no support and I believe I used brim. Print out 2, some force will be required to push it into Hatchbox spindle.