INSTALL INTO YOUR WALL: This pet door is best for homes where it might not be possible to install a pet door into your human door DURABLE FRAME WON'T RUST: Our pet door is made out of durable plastic that wont rust like other steel options while also providing great insulation TELESCOPING DESIGN FOR WALL INSTALLATION: Telescoping tunnel lets you use the door in walls that are 4 3/4 - 7 1/4 in thick; compatible extension kits sold separately for walls thicker than 7 1/4 in DIY INSTALLATION: This do-it-yourself project easily installs in all types of interior and exterior walls; cutting template and step-by-step instructions are included ENERGY EFFICIENT: The double-flap provides weatherproofing and energy efficiency, and a slide-in closing panel adds extra insulation when your pet is not using it; PVC frame withstands UV exposure LARGE SIZE: Large size for big dogs up to 100 lb; flap opening measures 10 1/4 in W X 16 1/4 in H GIVES YOUR PET FREEDOM: Let your cats and dogs come and go on their own schedule perfect for potty breaks or play time U.S.-BASED CUSTOMER CARE: Our pet product experts are here to help you and your pet and are available by phone, email or chat if you have any questions QUALITY GUARANTEED: PetSafe brand has been a trusted global leader in pet behavior, containment and lifestyle innovations for nearly 30 years; we help keep your pet healthy, safe and happy