Radius gauges can be used to measure radius values in reverse engineering. However, how can you acquire accurate measurements if a fillet face is distorted or if the value is not constant along the edge? This video shows a tool in Design X that can measure variable fillets in a few simple steps.

http://cimquesttv.wistia.com/medias/ntg0mdrrd7?embedType=async&videoFoam=true&videoWidth=640