Spring Drive Chronograph Evolution 9A Spring Drive Chronograph GMT in the Evolution 9 Style SBGC251 measures 45. 3mm in diameter, 15. 8mm in thickness, and 52. 6mm lug to lug. The case and bracelet are made of High Intensity Titanium, which is 30% lighter than steel while being more impervious to scratches and corrosion. The bezel rotates in both directions without a click, and has a sapphire insert with a 24 hour scale. The chronograph pushers have been made smaller while remaining