The comments made by Jay J, are incorrect. Andersen Corp. (America's largest window manufacturer, 101 years in business), spent tens of millions of dollars to invent and develop Fibrex material. Fibrex is a composite of wood fibers and thermoplastic polymers. It is not made up of "saw dust and scrap vinyl". Renewal Fibrex windows are one of the most tested and certified products in the window industry. It is tthe only Green Seal certified window in the U.S., Energy Star rated, NFRC tested and labled. Fibrex looks like a fine wood window, but is virtually maintenance-free. Up to 3x stronger than vinyl. Renewal by Andersen is the one of the top three selling replacement windows in the U.S. and will be #1 in 2004. Andersen is known for top shelf quality and customer satisfaction. This product is simply incomparable.