Luminox Men's A.1879.BO 1820 Series Quartz Sapphire Glass Black Watch Swiss Quartz Movement Field Series Swiss-quartz Movement Case Diameter: 42mm Water resistant 200m (660ft):in general, suitable for professional marine activity and serious surface water sports, but not diving Quartz movement Case Diameter: 47 Case back: Screwed Crystal and glass material: Sapphire glass anti reflective coating Water resistant to 660 feet (200 M): suitable for recreational scuba diving