Fiber-Metal 4118 face shield windows are injection molded from propionate, which is superior to other window materials in every major performance characteristic. They are preformed at the factory to the exact curve specified crown protectors for easy installation an exact fit and a perfect seal against dust, dirt and debris. The Fiber-Metal 4118 series is 8" x 11-1/2" x .060", is made to fit F300 crown protectors.