This is a USB drive inside a fidget spinner I originally designed for my son (now used by my wife).
More details on my blog at https://nirrobotics.com/2017/05/the-usb-spinner/
It uses a 4x13x5mm 624 bearing, a USB drive of the kind used inside just about any drive you get from AliExpress and 2 1/4" nuts as counter weights.
Print 2 of the "top" stl, one of each of the others, I printed everything in PLA except for the "cover" that I printed in TPU
When printing you need to pause the print just before the layer that covers all the internal holes (they all end at the same height to make this possible) and insert the bearing, dive and nuts