Citizen Eco-Drive Promaster Professional Diver is used for mixed gas diving with… its 6mm non-reflective curved crystal, ratcheted elapsed-time bezel, screw-back case & screw-down crown, and reinforced urethane band and extender, with a carrying case for the wetsuit strap extension. Crafted in stainless steel with luminous accents, and 300M WR. Featuring our Eco-Drive technology – powered by light, any light. Never needs a battery. Caliber number B873.