Citizen Promaster Air in black stainless steel case that holds a blue ion-plated rotating bezel with a professional calculator function and tachymeter on a blue dial with luminous hands and markers and a sapphire crystal. Atomic time clock synchronization for superior accuracy, a 1-second chronograph that measures up to 60 min, and a perpetual calendar. The black polyurethane strap fastens with ease. Water resistant to 200M. Powered by Eco-Drive so it will charge by any light and never needs a battery. Case size 46mm.