Audemars Piguet Royal Oak Men’s Watch Blue Stainless Steel 26240ST. Audemars Piguet’s Royal Oak delivers beauty by combining the modern colors of stainless steel and blue. The 41 mm case is assembled with a Grande Tapisserie dial in the iconic Bleu Nuit, Nuage 50 color. Powered by the self-winding 4401 calibre, this timepiece has a 70-hour power reserve.