The Truss Rod Gauge & String Action Gauge Bundle contains Music Nomad'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 Music Nomad's Precision Truss Rod Gauge which 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 Music Nomad’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.