The size of the aperture 'round open window' is expressed with f / number. For example: f / 2.8, f / 4, f / 5.6, f / 8, f / 22 etc. In the selection of this number series, the size of the window will be

The “Red” Sub, one of the most historic vintage pieces that was made by Rolex. I recall around 12 years ago when I started my career as a watchmaker glancing over at my first Submariner. I thought to myself,