A single pole module of a circuit breaker is disclosed. The housing includes a first portion and a second portion, and an interior wall separating the first portion from the second portion. The first portion includes a first section receiving a circuit board and a second section receiving a lever mechanism. The second portion includes a first section receiving an electromagnetic protection device, a second section receiving an arc extinguishing device, a third section receiving a thermal protection device, and a fourth section receiving an operating mechanism. The first and second sections of the first portion occupy substantially half of the housing and the first, second, third and fourth sections of the second portion occupy substantially half of the housing and the second section of the first portion and the third section of the second portion are opposite each other.