Amazon.com: String Action Ruler Gauge Tool for Electric Bass and Acoustic Guitar : Musical Instruments
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Amazon.com: StewMac String Action Gauge And Ruler, Metric, Stainless Steel - Designed by StewMac, The Original measuring tool for acoustic and electric guitar, and bass setup : Musical Instruments
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Guitar String Action Gauge Set Up Ruler for Electric, Acoustic, Bass, Classical Guitar - Imperial and Metric Measurements - 500 Micron Anodised Steel - MADE IN UK : Amazon.co.uk: Musical Instruments & DJ