The "black box" is a small lightweight passive volume control unit that plugs right into the end pin jack or output jack of your guitar. it is designed to work with virtually any acoustic instrument that has a pickup system, but lacks a volume control. housed in a rugged die cast black aluminum box, the black box is an almost bullet-proof design. it is extremely rugged. the "black box" measures only a scant 2" x 1 1/2" x 1 1/4" in size. weight: only 3 ounces.