Boat Porthole 21x 25in Aluminum Alloy Push Out Type Smoky Gray Tempered Glass Port Hole Window Skylight for Yachts RV1Corrosion Resistant: The overall frame is made of heavy aluminum alloy, and anodized surfaces are polished for a matte texture and corrosion resistance, will not be eroded even in harsh offshore or outdoor environments. 2Tempered Glass: The skylight glass part is made of 6mm thickness smoke gray tempered glass which filters out ultraviolet rays while ensuring that light can enter the cabin, improving the brightness of the cabin, and can also be used for ventilation Windows. 3Waterproof: The porthole frame is equipped with waterproof rubber rings to provide complete sealing and waterproof performance and shock absorption performance when the window is closed. 4Push Out Opening: The porthole can be opened at will in the range of 090 degrees, and equipped with 316 stainless steel support rod and hinge, providing fixed support at any Angle. Good for boat, yacht, ship, and RV. 5Multipurpose: Portholes can be used for sunroof, escape window, storage compartment, roof, or any location modification and retrofitting projects, with 21x25 inch appearance size, 18.4x22.4 inchxR45 mounting hole size, 12 inch thickness installation.