ammoon 4pcs Stainless Steel Guitar Notched Radius Gauge Fingerboard Fretboard Measuring Tool Set Notched Radius Gauge design can use with strings on. 7.25, 9.5, 10, 12, 14, 15, 16, and 20radii. Include 2 narrow radius gauges and 2 wide radius gauges. Set of 4 pcs stainless steel measuring tool for Guitar fingerboard.