Citizen Eco-Drive technology harnesses the power of light from any natural or artificial light source and converts it into energy which is stored in a rechargeable lithium-ion cell. It recharges continuously in any kind of light to run forever. 44mm x 12mm Polished/Brushed Stainless Steel Case – Scratch Resistant Sapphire Crystal – One Way Rotating Elapsed-Time Bezel – Screw-Down Crown – Solid Caseback.