SET Electric Violin Bridge Pickup Preamp for 4/4 Violin If you're a violinist this high quality bridge, pick-up and preamp kit is just the thing for amplifying your instrument's sound. This is a brand new set which comes complete with battery box, battery, connection cables, nuts and washers and wiring diagram Cmpatibility: 4/4 violins , Function : 1V + 1T Active , Input Impedance : 10M Frequency Response : 20Hz ~ 20KHz , Headphones :  3.5 Pick-up dimensions: 49 x 9.5 x 5.3mm , Bridge dimensions: 18 x 40 x 4mm Preamp dimensions: 58 x 43 x 18mm , Battery box dimensions: 81 x 22.5 x 31mm