1. Larger Cats for Stronger Breeds: Own a big cat like a Maine Coon, Burmese, Egyptian Mau? This cat door fits most cats. 2. The safest cat door you can find: Most pet doors for cats are secured with flimsy tape. But this kitty door is held securely with strong screws. 3. Installs in minutes; stays snug in place. 4. Keep Big Dogs Away: This big cat door prevents your big dogs from getting into cat food and litter. 5. No Annoying Flip: Ever tried training your cat to use a pet door with a flap? It's a frustration. Luckily, our cat doors are flapless, so your pudgy feline can walk right through. FITS SOLID AND HOLLOW CORE DOORS: Unlike most large cat doors, our cat doors are suitable for interior doors. The unique design keeps the cat's claws from getting stuck in the hollow door. Material: ABS Plastic Frame Size: Height 22.5cm Width 27cm Thickness 5.5cm Inner Frame Size: Inner Diameter 17.5cm Inner Groove Thickness 3.5cm Package Included: 1 Set of Cat Doors (with Screws and Screw Caps) Warm Reminder: Because of the thickness of each door The screws are different. If the screws are not suitable during installation, they need to be purchased separately. It can be directly glued to the glass with glass glue.