9-piece understring radius gauge set - Sizes: 7.25, 9.5, 10, 12, 14, 15, 16, 17, 20 inches - Material: stainless steel for strength and durability - Purpose: measure the radius under the strings and accurately configure guitar bridge saddles to match the fretboard radius - Easy to use: simple under-string radius measurement for quick setup and adjustment Benefits - Precise radius matching between fretboard and bridge saddles for consistent action and better intonation - Durable stainless steel construction for long-term reliability - Compatible with common guitar radii and easy to select the correct gauge quickly Use scenarios - New setup: after installing a neck with a known fretboard radius (for example 9.5"), pick the matching gauge and adjust the saddles to align with the fretboard curvature - String change or neck adjustment: re-measure to verify saddle configuration remains correct and re-tune action and intonation accordingly - Professional repair or luthier work: quickly verify radius on multiple guitars to ensure saddle geometry is accurate before setup or replacement