One pole provide protection against surge current of circuit single phase 220V.

Two pole provide protection against surge current of L and N phase to earth of circuit single phase 220V resulted from lightning.

Three pole provide protection against surge current of S phase of TT, TN-S system 380V, and also protect S to earth of IT TN-C system of 380V

Four pole provide protection against surge current against S, N to earth of TT TN-S system of 380V.