Be careful, a lot of SG90 servos are fakes. Below a certain price, they all appear to be counterfeit.
As far as I can tell, the real ones have four screws in the base, and "TowerPro" printed into the plastic on the top. The fakes have two screws, no brand name moulded into the plastic, and inevitably stop working quite swiftly.
https://brachiograph.readthedocs.io/en/latest/explanation/ha...