ammoon 9pcs Guitar Bass Understring Radius Gauge Luthier Stainless Steel Tool Set Bridge Saddle Adjustment with Pin Puller 9pcs Radius gauges come in sizes: 7.25" 9.5" 10" 12" 14" 15" 16" 17" 20". For electric guitar, electric bass, electric guitar, acoustic guitar fretboard. Easy to measure the radius from either above or below the strings, and come with Pin Puller. Using the matching top radius of this gauge to determine the proper height adjustment for the bridge saddles.