This spec is an example of balancing board for a battery pack contains 6 polymer lithium ion batteries (rated 4.2V) in series. We also have balancing board for battery packs with 3-17 cells (common types like 3.6V, 3.7V, 4.2 etc) in series connection
The upper one is sealed with metal shield, which provide extra protection and heatsink for the balancing board
The lower one shows the inside structure. Each battery cell is monitored/protected by complete circuit.
The high lighted fields are the key parameters when choosing a battery balancer.
Because now most battery cells are made to a standard, in most cases, to choose a battery protector, user only need to know how many cells are in the battery pack, and what is the cell type.
Usually user can pick a protector by "My battery pack is using xx cells of xxV in series"