MARINEMASTER SPRING DRIVE PROFESSIONAL. Hand winding capability. Power reserve indicator. Power Reserve: approx 72 hours. Accuracy: +/-1 second per day. 30 jewels. Sapphire crystal with anti-fogging coating. Screwdown caseback. Silicone strap with buckle. Water Resistance: Diver's Watch 600 meters (2440 feet). Meets ISO standards and is suitable for scuba diving. Case Diameter: 50.7mm. Black Ion Finish. High-intensity Titanium Bezel and Inner Case. DLC finish high-intensity Titanium Outer Case