A composition comprising a polysiloxane polycarbonate block copolymer; a cycloaliphatic polyester; and a polycarbonate that is different from the polycarbonate block copolymer, having a weight average molecular weight of less than about 20,000 Daltons. The compositions have high flow at low temperatures and good impact properties. The compositions are useful for the manufacture of components for handheld electronic devises such as cellular telephones.