Fibre-Metal® face shield windows are injection molded from propionate, which is superior to other window materials in every significant performance characteristic. They are pre-formed at the factory to the exact curve of our crown protectors for easy installation, an exact fit and a perfect seal against dust, dirt and debris. All High-Performance windows are 0.060″ thick for an extra margin of protection, yet they cost no more than ordinary 0.040″ thick windows.