The Deye BOS-B accessory kit ("base box") holds the mechanical parts and cables for one Deye BOS-B Pro battery cluster of up to 16 modules (DEYE-BOS-B PRO-16.08KWH).
BOS-B Pro modules don't go in a rack: they stack on the kit's four bases, up to four stacks of four, with the control box on top. The kit supplies the bases, feet and covers plus every interconnect cable between stacks, the control box and the inverter.