MagiDeal Guitar Notched Radius Gauges for Measuring Fingerboard Radius Pack Of 4pcs Material: Carbon Steel Color: Silver Handy when you want to check a fingerboard without taking the strings off The set includes closely-spaced string notches for use near the nut (narrow), and wider spacing for use near the body (wide) The radius gauges comes in all popular fingerboard radii. (7.25", 9.5", 10", 12", 14", 15", 16" and 20")