Description: 【HIGH QUALITY】: Nautical slide rule is made of high quality PP material, durable. 【PERFECT DESIGN】: The air is flowing and the ship is moving forward. The actual wind "Wind" and the wind caused by navigation "navigation wind" are superimposed so that the anemometer on ship can only measure the "synthetic wind" of the two.Generally use the "Wind calculator" to obtain the Wind. 【FUNCTION】: Ships sailing must keep abreast of the changes in the wind and cloud to ensure the safety of navigation. 【USAGE】: Point the wind direction and wind speed of the synthetic wind and sailing wind to the corresponding points on the calculation disc, and then rotate the moving disk on the calculation disc so that the line connecting the two points is parallel to the longitudinal line of the calculation disc chassis to read the Wind direction, count the Wind speed. 【APPLICABLE】: Suitable for sailing, marine, etc. Specification: Material: PP Size Chart: Diameter: 10cm / 3.94inch Package Includes: 1 Set Nautical Slide Rule Note: Please allow slightly errors due to manual measurement and different monitors.