All Window kits are easy to install and require a simple rectangular enclosure cut-out. They are ideal for indoor and outdoor Type 3R, 4 and 12 applications. Stainless Steel Window Kits are ideal for indoor and outdoor Type 3R, 4X and 12 applications where corrosion is a concern. Non-Metallic Window Kits are ideal for indoor and outdoor Type 3R, 4, 4X and 12 applications. They are also ideal for non-metallic enclosures where exterior metallic materials are not allowed and can accommodate up to .25-in. enclosure material thickness. When determining if a window kit will fit in a door or cover, be sure to allow for gaskets, data pockets, door handles, latch rods and other parts attached to the door or cover.