Duality for SU x SO and SU x Sp via branes

Using a six-orientifold, fourbranes and four fivebranes in type IIA string theory we construct N = 1 supersymmetric gauge theories in four dimensions with product group SU(M) x SO(N) or SU(M) x Sp(2N), a bifundamental flavor and quarks. We obtain the Seiberg dual for these theories and rederive it v ia branes. To obtain the complete dual group via branes we have to add semi -infinite fourbranes. We explain the addition of fourbranes as a reverse of higgsing.