Omega Men's 3513.50.00 Speedmaster Automatic Chronograph Watch Quality Swiss Automatic movement; Functions without a battery; Powers automatically with the movement of your arm Scratch-resistant sapphire crystal with anti-reflective treatment inside Case diameter: 39 mm Stainless-steel case; Black dial; Date function; Chronograph functions; Tachymeter function Water resistant to 165 feet (50 M): suitable for swimming and showering