SIZE: There are 9 sizes of universal under-string radius gauges, which are 7.25" 9.5" 10" 12" 14" 15" 16" 17" 20" and can be used to measure different instruments. The measurement range is wide. EASY TO USE: These popular fingerboard radii can easily measure the radius above or below the strings, and can quickly and accurately adjust this bridges saddle. The method is simple to use, which brings convenience to your bridge saddle adjustment. METAL APPEARANCE: The universal under-string radius gauge is made of good metal materials. The appearance is silver, sturdy and and can be used for a long time. Guitar radius gauge is a good tool for measuring string instruments such as guitars. SCOPE OF APPLICATION: The guitar radius gauge can accurately measure the fingerboard radius of musical instruments. Guitar radius gauge is suitable for all kinds of electric guitars, electric basses, acoustic guitars, electric box guitar fingerboards, and tuning codes in radians. QUALITY SERVICE: If you encounter any quality problems or usage problems after purchasing our guitar string lower radius gauges, please feel free to contact our customer service staff, we will be happy to serve you!