The 123electric BMS-boards are interconnected with a soldered single-wire, which makes mounting less time-consuming, and very reliable. The 'IN'- and 'OUT'- boards connect via a twisted-pair to the BMS-controller (or, in case of sub-divided battery-packs, to the next-in-line).
For a single pack of say 32 batteries, the system would consist of:
1 BMS-'OUT'-board
30 ordinary BMS-boards (not included, seperately sold)