Sumnacon Guitar String Action Ruler Gauge Tool - Stainless Steel Double Sided Multi Function Guitar Luthier Accurate String Measurement for Electric Bass and Acoustic Guitar Stainless Steel, Durable, Beautiful and Widely Used Pocket Sized, Convenient for Taking to Everywhere You Like Double sided, Imperial (inches) One Side, Metric (millimetres) On The Other. With Conversion Chart of String Action at 12th Fret Printed. Use To Measure: Nut / String / Bridge / Pickup Pole Piece / Saddle Height Plus Saddle Slot/ Fret Slot Depths Perfect Accurate Action Measurements for String Instruments Such as Guitar, Bass, Mandolin, Banjo etc