If C C is a nuclear C β {C^*} -subalgebra of a C β {C^*} -algebra A A , then we have C β D = ( A β D ) β© ( C β B ) C \otimes D = (A \otimes D) \cap (C \otimes B) for any C β {C^*} -algebras B B and D D with D β B D \subset B . Using this, we show that if A A and B B are AF algebras and A β F B = A β B A{ \otimes _F}B = A \otimes B , then either A A or B B must be subhomogeneous.