Appearance - the appearance of door window is also the key link, cr aluminum door have artificial oxide film and coloring formation on the surface of composite membrane layer, this kind of composite membrane not only corrosion resistance, wear resistance, and have certain fire prevention function, high gloss, when the choice to the comparison of as much as possible, try to choose normal aluminium alloy the product of manufacturer of door window, select the processing precision, accurate, flexible and convenient opening and closing  No noise, and elegant decorative effect of the product.