Abstract: The invention provides a composite part comprising a matrix and coated, hollow microspheres. The coated, hollow microspheres are generally polymeric spheres with an inorganic exterior coating such as calcium carbonate. In one embodiment, the composite part is a fenestration component formed by a pultrusion process, and may include reinforcing fiber material such as roving or mat. In some embodiments, the matrix is made from a curable precursor that includes a thermosetting resin and coated, hollow microspheres. A method for making a pultruded composite part incorporating coated, hollow microspheres is also provided.