Audemars Piguet Royal Oak Men’s Watch 41MM Gray Stainless Steel 15500ST. 50 m (5 ATM). Audemars Piguet improved their classic Royal Oak series with the introduction of the 15500 series. This new series features wider indexes, a date window positioned farther from the center of the timepiece, and a minute track printed on the external area of the dial. The watch has a 41mm stainless steel case that is 10.4mm thick, with glare-proofed sapphire crystal and a screw-locked case back. The dial is an elegant slate grey with a Grande Tapisserie pattern, luminescent white gold applied hour markers, and hands. It is powered by the self-winding 4302 Caliber, providing date functionality and a power reserve of 70 hours. The Royal Oak is presented with a stainless steel bracelet and fold-over clasp, and has a water resistance of 50 meters (164 feet).