Fits some 4-string electric bass, for top-loading and string-through-body combined usage Total string spacing: 19x3mm=57mm (2-1/4 inch), 4 mounting screw holes spacing: 19x3mm=57mm (2-1/4 inch) Made of high density zinc alloy, well finished,stable and durable Pre-radiused base plate for more precise adjustment and better intonation