The Truss Rod Gauge and String Action Gauge combo pack contains MusicNomad's two most popular precision gauges. Measuring your neck relief and string action height are the two most common tasks performed to improve your guitar or bass playability and sound. The first step is to use MusicNomad's Precision Truss Rod Gauge that comes equipped with the three most common relief measurements (.006”, .008”, .010”). Instructions printed right on the handle make it extremely easy to dial in your neck relief. The second step is MusicNomad’s Precision String Action Gauge that comes with accurate measurements that are easy to read with the black finish contrasted with deep etched white markings. Measurements are in inches, metric and 64ths to customize to your preference. A convenient chart on proper height by instrument type takes out the guesswork. Both gauges are designed for all electric, acoustic, classical and bass guitars.