This is a MASTERY BRIDGE M1, which I used on a Fender USA Mustang. It's in good condition, as I've had it installed for about six months. ■ Bridge for Jaguar/Jazzmaster, Mustang ■ USA Standard ■ String spacing (E to E): 52mm ■ Mastery Bridge is a replacement bridge that can be installed on Jazzmaster, Jaguar, Mustang, Bass VI, Jag-Stang, and Telecaster models equipped with a Bigsby tremolo. It prevents strings from coming off the saddle even during intense playing, and also achieves a beautiful, resonant tone that brings out the full potential of the guitar. ※ ・ "M1": For American-made guitars, including Fender USA. The diameter of the hole for inserting the bridge foot is "0.310 inches (approx. 7.874mm)". - Included: Main unit, cloth bag, three types of Allen wrenches, original pencil, tin case - Material: Metal - Type: Guitar bridge Thank you for looking.