The Audemars Piguet Royal Oak Extra-Thin Selfwinding Flying Tourbillon Chronograph (RD#5) 39mm (ref. 26545XT.OO.1240XT.01) is an automatic sport watch, with a 39mm titanium case, powered by the 8100 movement and a 72-hour power reserve. Water resistance is rated to 20m, under a sapphire crystal.