At that time, Sunn was in its "mix and match" mode. All cabinets and heads were sold separately. The Concert Bass head was recommended with the 115S, 215S, 312S, and possibly with the 412S, 610S and 612S as well. I think the 215S was the most common choice, though. That's what I had for a while. For portability and flexibility, I'd have preferred two 115S cabinets, though.