A molded article is provided that has a resin matrix having a surface, the resin matrix formed from cross-linked polyester resin or vinyl-ester resin. Glass fibers are crossed linked to the resin matrix via a silane coupling agent reactive with the matrix. A molded article is provided that has a resin matrix having a surface, the resin matrix formed from cross-linked polyester resin or vinyl-ester resin. Glass fibers each covalently bonded to at least one microspheroid matrix via a silane coupling agent reactive with a surface of the at least one microspheroids are present in increase the fiber pull strength. A sizing composition for treating glass fibers is also provided for use in such articles.