Encourage exercise and independence: Give your cats and dogs freedom to go in or out without asking for your help to open the door—perfect for potty breaks or play time | Easy to install: Snaps directly into your existing screen door, window or porch screen for quick and easy installation, and blends perfectly with your existing screen | Built to last: The high-impact plastic frame surrounds a durable mesh that is puncture and tear-resistant to withstand frequent use from your pets; Large door is reinforced with fastening screws | Safe and secure: Large door has sliding wind-locks that are strong enough to resist flapping open in the breeze but not so secure that your dog can’t run through; small door locks to prevent entry | Dimensions: For pets up to 100 pounds; Flap opening size is 10 1/4 inch W x 17 1/8 inch H; Measure your pet to ensure comfortable use | Size information: For pets up to 100 pounds, the large flap opening size is 10 1/4 inch W x 17 1/8 inch H; Measure your pet to ensure comfortable use | Quality guaranteed: PetSafe brand has been a trusted global leader in pet behavior, containment and lifestyle innovations for nearly 30 years; We help pets and their people live happy together