Rolex 4030 is a calibre by Rolex.
This self-winding chronograph movement bases on the calibre El Primero by Zenith (Calibre Zenith 400) and has been modified by Rolex.
The fast-oscillating Zenith calibre has been clocked down from 36,000 A/h to 28,800 A/h and has been provided with a Breguet hairspring and with microstella screws.
It was used in the model Rolex Oyster Perpetual Cosmograph Daytona till 2000. Afterwards it was replaced by the Rolex-own development Rolex 4130.