Flight computer. Whiz wheel. E6B. Regardless of what you call it, this manual calculation/conversion tool is a fundamental item for pilots of all experience levels. With this heavyweight fiberboard Flight Computer, you can easily determine wind components/crosswinds, true airspeed, density altitude, time/speed/distance parameters, and much, much more. The 9" x 4½" tool is capable of performing several unit conversions, and includes both nautical and statute mile scales. It also includes an instruction booklet and comes in a sturdy vinyl case. A must-have item for all your aeronautical performance calculations - batteries not required!