This was used on a bass that I sold a while back. Just been sitting in the drawer. Don't need it , but I was intrigued by Variable midrange. 2 Concentric Pots Bass/Treble Mids/Freq. The BQC Control features a bass and treble equalizer on a concentric (stacked) pot along with the concentric (stacked) mid-control. It takes up very little space and will work with any pickup, active or passive. It comes complete with knobs including 2 extra volume knobs. Paypal $65 includes shipping!