1. No need for batteries, driven by spring, easy to use, similar to the operation method of a quartz clock2. There are two movements, left and right. The error is about 3 minutes3. Material: plastic shell, zinc alloy movement4. Maintenance: the chess clock should prevent contact with corrosive objects, avoid exposure to the sun, rain, drop and close to a strong magnetic field 5. Size: about 15x5.5x9cm6. Weight: about 280 gramsHow to use:1. Put the chess clock on a flat table before use2. Press the back cover The direction indicated by the arrow is enough to wind up the mainspring. After the mainspring is tightened, do not turn it hard to avoid damage. 3. Set the needle: first set the minute hand to the 12 position, and you can also set the minute hand to any indicated position as needed. When setting the hands, be sure to move the clock at the vertical position, so as to avoid the minute hand being stuck on the indicator flag and causing the minute hand to shift4. Start: Press the left button, the left clock will stop and the right clock will start, press the right Press the button, the clock on the right will stop and the clock on the left will start (but it is not advisable to hit the button hard to avoid damage)5. Speed adjustment: If there is a speed error, use a small metal rod in the direction pointed by the left and right of the moon-shaped hole on the back cover Toggle the speed mechanism in the hole to adjust