Product Description: Quantity: one piece Net weight 20.6 grams Gross weight 24.5 grams Package size: 9.5 x 5 x 1.5cm. Product size: 9.5*4.5*1cm white box packaging How to use the instrument of measurement: As the scroll wheel rotates between two points on the map, the distance measurement pointer rotates accordingly. Record this value according to the corresponding scale and multiply it by the scale coefficient to get the actual distance between the two points, which is more accurate than the straight line distance measured with a Many ruler; the map distance counter is convenient and quick to measure the mileage distance, and it is specially used to measure the actual distance of the curved route on the map. Precautions: 1. Use it in a horizontal state to ensure accuracy as much as possible; 2. In order to avoid confusion with the magnetic needle, please keep a certain distance from barbed wire and magnetic objects when using it. 3. Do not hit the object with a survey ruler, so as not to affect the measurement accuracy. 4. Keep the disc surface and lens clean, do not wipe them with a cloth or dirty hands; 5. It should be closed when not in use and should not be placed near ferromagnetic substances to prevent loss of magnetism. High Quality: This mini navigation outing Curvimeter is made of premium quality metal and plate, solid, durable, rainproof and long lasting. This lightweight and portable dungeon, with a mini metal replacement for easy holding Diance measurement: This multi-function cartographic diance measuring gauge can help you quickly calculate the diance by measuring the diance between two points on the map. Wide application: these Map Calculator Compass Gauge is a nice replacement gift for people who love outdoor activities, such as hiking, travelling, camming, backpacking, etc. Easy to use: the diance calculator Metal Wheel Mapping TOOL e easy to use, play the mini metal wheel on the map and the roller, the pointer would show the exact scale