Generally speaking, the larger the window, the narrower and thus more fragile the frame. Bayer MaterialScience has the solution: composite fiber materials based on polyurethane. Bundles of glass or carbon fibers are sheathed in the Bayer plastic, shaped under heat and fabricated into frame components. The results are impressive. Unlike wood or PVC, the frame is weather-resistant, resists wear, does not become brittle and is extremely break-resistant.