Ruggles Scales make it easy and affordable for you to compute weight and balance on your own aircraft any time and any place. They are small and easy to transport. With their drive on capability, there is no need to jack up each wheel to slide scales in place. Ruggles Scales use the principle of a fulcrum and a very long lever. So simple, the only tool you will need is a screwdriver for calibration. Sturdily constructed of cadmium plated steel and precision engineered for accuracy. Complete instructions are included with scales. Not certified. Capacity is 3600 lbs. (1200 lbs. per wheel). Scale can be set to either 2:1 or 4:1 ratio. Tricycle gear set includes 3 arms and 3 scales. Taildragger set includes 2 arms and 3 scales.