Features: Tighten the spanner holder on the back of the guitar head to holds the key in a safe place, very handy tool to holds key. Make of metal materials, it is sturdys and wear-resistance, and can be used for a long terms. Easy to remove, no tool or knobs are needed to remove and return the key. Commonly used on electric guitar, locking tremolo system, tremolo bridge, and other acoustics instruments that require a spanner and have enough space to install a spanner holder. Come with mounting screws and two wrenches ( 2.50mm & 3mm). Specifications: Materials: Metal Color: Gold/Silver/Black Size: 2.5mm(0.98inch) and 3mm(0.12inch) Note: Please allow 1-2cm errors due to manual measurement, make sure that you not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1set Wrench Holder