Features:■The pocket-sized guitar string action ruler gauge is marked with scale to measure string height, bridge saddle height, saddle slot depth, pickup polepiece height, fret slot depth and nut height, with conversion chart of string action at 12th fret printed on one side.■4mm & 5mm ball end guitar truss rod wrench are made of carbon steel, durable and highly wear-resistant. Adjust the guitar neck straight. Suitable for Martin Acoustic Guitar or other guitar which couldn't reach it with a regular hex wrench truss rod adjustment.■The guitar allen wrench set has 9 different gauges: 1.5mm, 2.0mm, 2.5mm, 3.0mm, 4.0mm, 5.0mm, 1/20in, 1/8in, 3/16in. Various gauges make them versatile.■This is a specially wrench set for guitar bass neck bridge nut locking knob screw adjustment. Specification:Wrench size description:1.5mm for electric guitar & bass bridge.2.0mm for volume knobs.2.5mm for electric guitar bridge string block.3.0mm for nut locking.4.0mm & 5.0mm covered most acoustic guitar truss rod screw gauges, fit for that has deep or narrow truss rod likes martin guitar. Also suitable for standard truss rod guitar, likes yamaha, gibson, ibanez, etc..1/20 inch wrench fit for some guitar bridge which made in Japan. 1/8 inch wrench fit for some guitar bridge made in USA. 3/16 inch wrench fit for some guitar bridge made in Mexican. Packing List:1 x String Action Ruler Gauge1 x 4mm Ball End Truss Rod Wrench1 x 5mm Ball End Truss Rod Wrench1 x 1.5mm Wrench1 x 2.0mm Wrench1 x 2.5mm Wrench 1 x 3.0mm Wrench 1 x 4.0mm Wrench 1 x 5.0mm Wrench 1 x 1/20in Wrench 1 x 1/8in Wrench 1 x 3/16in Wrench 1 x Storage Bag