The Yacht-Master II is equipped with calibre 4161, a self-winding mechanical regatta chronograph movement entirely developed and manufactured by Rolex. The result of over 35,000 hours of development, the Yacht-Master II introduces a new regatta countdown with a unique, patented mechanical memory created by Rolex. A number of the 360 components in the 4161 movement are so tiny or complex that they can only be made by new, cutting-edge technology.
Like all Rolex Perpetual movements, the 4161 is a certified Swiss chronometer, a designation reserved for high-precision watches that have successfully passed the Swiss Official Chronometer Testing Institute (COSC) tests. Its architecture, in common with all Oyster watch movements, makes it singularly reliable.