Omega Men's 3539.50.00 Speedmaster Automatic Chronograph Watch Quality Swiss Automatic movement; Functions without a battery; Powers automatically with the movement of your arm Functions without a battery; watch powered automatically with the movement of your arm Scratch-resistant sapphire crystal Stainless-steel case; Black dial; Chronograph functions; Tachymeter function Water resistant to 330 feet (100 M): suitable for snorkeling, as well as swimming, but not diving