ENGINEERED FOR THICK WALLS: the Endura Flap single flap pet door is specifically designed for thick walls up to 13" deep and provides superior insulation, keeping your home comfortable and saving on energy costs; the flexible flap material remains functional in extreme temperatures, as low as -40 degrees; large flap measures 12" x 23" and is suitable for pets up to 36" tall SIMPLIFIED INSTALLATION & DURABILITY: This pet door features a strong aluminum frame and an innovative telescoping aluminum tunnel that makes installation quicker and easier than ever; the all-metal construction not only provides a cleaner, more professional finished look but also ensures it will not warp or wear from weather, guaranteeing a durable and secure entryway for your pet AESTHETICALLY PLEASING: available in sleek white or black aluminum frames to match your home's décor; our new advance design pairs a stylish modern frame construction with the established durability and performance of the Endura Flap SECURE AND VERSATILE: includes a robust locking cover, as strong as 1/16" sheet steel, allowing you to block access when needed, providing added security for your home; triple sided magnet design in the flap allows for flexibility when training or with timid pets LIFETIME GUARANTEE: our pet doors are proudly designed, engineered, and manufactured in the United States, with a lifetime warranty you can be certain your investment will provide years of enjoyment for you and your pets The Endura Flap Single Flap Pet Door for Thick Walls is a durable and practical solution for both cats and dogs of all sizes. The high-quality aluminum frame and polyolefin polymer flap withstand harsh climates, ensuring your pet door lasts for years. The flexible and safe Endura Flap remains functional in temperatures ranging from -40 to 100 degrees Fahrenheit. Superior wind resistance is provided by strong magnets lining the flap on three sides, resisting winds up to 50mph for a secure seal, protecting your home from drafts and energy loss. For added security, the pet door includes a sturdy locking cover, as strong as 16 gauge steel, that can be used on the inside or outside frame to block access when needed, perfect for nighttime or when you're away. The all-aluminum telescoping tunnel resists warping, weather, and wear, providing superior protection and a cleaner finished look. This makes installation a much easier, quicker process. No more brackets or taping: just cut the hole, slide in the frames, screw the tunnels together, and seal. Available in black and white, the Endura Flap Pet Door blends seamlessly with your home's aesthetic. Multiple flap sizes (small to extra-large) ensure a perfect fit for your pet, providing them with the freedom to come and go as they please. The taller, narrower flap design accommodates both large and small pets, allowing them to share the pet door comfortably. 100% designed, engineered, and manufactured in the U.S., this pet door is built to meet high-quality standards and is backed by a lifetime warranty and a 30-day return policy. Choose the Endura Flap Pet Door for a reliable, weather-resistant, and secure solution tailored to your pet's needs. Please note: This model is designed specifically for thick walls, accommodating wall depths between 7-1/2" and 13". It is not compatible with walls thinner than 7-1/2" due to the depth of the aluminum telescoping tunnel system.