This is a "bearing" for fidget spinners. It was modeled to be the same size as the 608 bearings commonly used in fidget spinners. The center hole is 8mm, so you should still be able to use thumb pads. The outer diameter is 22mm and therefore should pop into any spinner you might want to put it in. Finally the "bearing" is 7mm tall. There are 3 different versions. A loose version (called "bearing"), a tighter version ("bearing-tighter"), and a version with 4 cutouts ("bearing-slots"). There is always room for improvement. Video: https://youtu.be/UMClVU6S02A