Below is a list of Corrugated Fiberglass manufacturers from Spokane, Washington. Corrugated fiberglass is a fiberglass sheet that is shaped to have alternating parallel grooves and ridges that wave or ripple in a consistent pattern. Fiberglass products are composed of a matrix of glass fibers interwoven with a polymer matrix. Corrugated fiberglass products are generally composed of more than one layer and are among the most widely used and popular fiberglass reinforced plastic products.