The underwing gondolas were designed for the Bf-109 to replace some of the firepower lost when the F/G models were designed. The problem with the pods was that they adversely affected the handling of the aircraft. Still the addition of two 20mm cannons was desirable especially when dealing with enemy bombers.
The Eduard kit comes with two gondolas in the kit. They look nice but they are 2mm too long and don’t fit on the wing of the model. Well I’m glad to tell you that this is not the case with the Brassin ones. They fit the wing of the model perfectly.