Audemars Piguet Royal Oak Men’s Watch 41MM Silver Stainless Steel 15510ST. 100 m (10 ATM). Audemars Piguets Date Function adds a modern twist to the classic Royal Oak. The stainless steel 41 mm case is assembled with a screw-locked crown and a water resistance of 164 feet. Powered by the self-winding 4302 calibre, this timepiece has a 70-hour power reserve.