EFFORTLESS INSTALLATION: The Endura Flap pet door for sash windows is designed for an quick and easy installation process in your vertical sliding sash window, making it perfect for renters and vacation homes without permanent alterations ACCOMMODATE PETS OF ALL SIZES: With four different flap sizes available, this pet door is suitable for cats, small dogs, and large breed dogs, ensuring a perfect fit for your furry friend's needs; small flap measures 6" x 11" and is suitable for pets up to 15" tall ENERGY-EFFICIENT DESIGN: The pet door features a strong aluminum frame, insulating tempered safety glass, and a complete magnetic seal on the flap that withstands winds up to 50mph, ensuring your home remains comfortable and protected in all weather conditions INSULATION AND WEATHER RESISTANCE: The pet door comes with a draft stopper and weatherstripping to provide extra insulation and protection against the elements, keeping your home cozy and secure SAFETY AND SECURITY IN MIND: your pet door includes a durable molded ABS plastic locking cover to keep your pets safe and prevent unwanted visitors when you're away or during nighttime hours The Endura Flap Pet Door for Sash Windows offers an easy, non-permanent solution for pet owners who want flexibility. It fits securely into vertical sliding sash windows within minutes, making it perfect for renters or vacation homes. This door is designed for convenience, with LoE premium glass for excellent insulation and a heavy-duty aluminum frame for durability. Installation is simple and tool-free. Just place the pet door in your window, adjust the spring-loaded extender, and secure it by lowering the sash. It includes weather stripping and a Draft Stopper to ensure a snug, weatherproof fit.