The Shadow SH SB2 Twin Disc Transducer for Upright Bass is a double side disc transducer that mounts either between the wings and the feet of the bridge or between the feet and the instrument"s top. You can shape the tone by mounting your Shadow Twin Disc transducer on your bass where it produces the sound you like best.2 upright bass transducer with 1/4" socket Mounting adhesive Copper foil tape Easy installation Includes an attached 1/4" (6.3mm) output socket