Only fits Fenders with imperial threads on the saddles (American). Does not fit Gotoh bridges or other Far East manufacturers make that feature on some Mexican or Squier P basses (you'll need M3x15mm set screws for those).
Fits the saddles of a MIM Fender Precision Bass. I needed to put some PTFE tape in the threads to stop them rotating with the vibration of playing. The old ones jumped out because of this.