Prospex Black Series. Designed for those who treat life as the ultimate adventure, Seiko Prospex keeps moving forward, meeting every challenge with technological excellence and winning design. Featuring “Green LumiBrite Pro, " developed for divers by combining the color most recognizable in the dark with a higher brightness and longer afterglow, this extraordinary timepiece provides a "night vision" experience for visibility in the dark resembling the view seen through a night scope. The striking dark gray dial also features a magnified day/date calendar and is framed by black ceramic uni-directional rotating elapsed timing bezel. Following ISO standards for scuba diving, this Prospex Black Series model offers a stainless steel case and bracelet with black hard coating, a design based on one of Seiko's most iconic diving styles, and includes a screwdown crown and caseback, a sapphire crystal with anti-reflective coating on the inner surface, and a tri-fold push button release clasp with secure lock and extender. For reliable timing in rough waters, the 24-jewel automatic movement beats at a frequency of 21,600 vibrations per hour, with a power reserve of approximately 41 hours and manual winding capability. 200m Water Resistant