1.Small, lightweight and portable.Professional Multi-function High Precision On-board Compass.2.Great for marine, vehicle, boating, traveling, hiking, outdoors, etc.The outer tick of outer ring is CM ruler. The pointer rotating a week is a cm.3.The inner tick of outer ring is 1: 50,000 scale, applying to the 1:50,000 map.4.The outer tick of inner ring is 1: 20,000 scale, applying to the 1:20,000 map.5.The inner tick of inner ring is 1:5,000 scale, applying to the 1:5,000 map.Instruction:Move the pointer to zero, i.e. at the scale of 1:1.Align the small wheel to the measuring address, slip(rolling) to the destination along the route.According to the map scale, read the number of kilometers on the odemoter.Material: Aluminum alloy + ABScolour: blackPackage Contents:1 x Map Rangefinder OdometerOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.