Quantity: one piece Color: Black Product size: 15 x 5.5 x 9 cm Packing box: 19X7X12CM The net weight of the chess clock: 280 grams, + color box is 350 grams This chess clock does not require batteries, is driven by a mainspring and is easy to use, similar to the operation of a quartz clock. br Material: Plastic Case, Zinc Alloy Movement Technical Indicators: The product is divided into left and right movements, and each complete spring can last no less than 36 hours. The daily travel time accuracy error is 3 minutes. The method of use is as follows: 1) Place the chess clock on a flat table before use 2) Press the direction indicated by the arrow on the back cover to fully wind the mainspring. After the mainspring is tightened, do not twist it hard to avoid damage. 3) Set the hand: first set the minute hand to the 12th position, or set the minute hand to n any position indicated, if necessary. When adjusting the hand, be sure to turn the clock to the vertical position to prevent the minute hand from getting stuck on the indicator flag and causing the minute hand to drift. 4 ) To start up : Press the left button, the left clock will stop and the right clock will start, press the right button, the right clock will stop and the left clock will start (but it is not recommended to press the button hard to avoid damage) 5) Speed adjustment: If there is a mistake in the speed, use a small metal rod to adjust the speed mechanism in the hole in the direction shown on the left and to the right of the moon-shaped hole in the back cover. maintenance: The chess clock should be protected from contact with corrosive objects, avoid exposure to sunlight, rain, dropping and near strong magnetic fields