Zuanjia Double Sided Multi Function String Action & Guitar Set Up Gauge Ruler ~ With User Guide & Free Holder ~ Luthier Tool for Electric, Acoustic & Bass Guitars ~ Inch & Millimeters Measures: String height. Pickup Height. Bridge saddle height. Saddle slot depth. Fret slot depth Nut height. With user guide sheet. Free plastic holder ~ Very Accurate and Clear. Simple & easy to use. Also Suitable for other stringed Instruments. Credit card size and shape for easy and convenient storage and transport High Quality. Made of durable Stainless Steel with etched printing which will never wear off. Features a string action setup guide. Perfect for setting up your guitar to suit your personal taste. Easy to use whether you are doing your first guitar setup or are a professional luthier.