The regular size spinners with skateboard bearings are too big for my young kids to spin in their hands. Their fingers just aren't long enough to give it room to spin. So I designed a mini-spinner that works great for small hands. The photo shows this mini spinner next to a full-size version I found elsewhere on thingiverse (I didn't design the bigger one).

This one uses 4x11x4 bearings. I had a few leftover after changing out the extruder contraption on my printer, so I made this to put them to good use. Print two of the bearing caps to press into the middle of the center bearing to give it something to hold on to while it spins.

The holes are designed to exactly fit the 11mm bearings. If your printer struggles a bit and you find the fit is too tight or too loose, you might want to print it just slightly bigger or smaller in your slicer to make it fit.