RadialMate™, a 3.5" clear 20 mil plastic compass rose allows you to instantly read a desired course by placing the product over any sectional, chart, or graphic. No reciprocals to calculate. RadialMate™ comes with a hole in the middle, allowing additional use as a string compass. Its conveniently sized to fit in your pocket. RadialMate™ also contains Safe Flights vertical scale that measures mileage for WAC, SEC, TAC, NOS, JEPP & ELA charts, eliminating the need for that ruler you can never find.