Size: This is a large cat door, external size: 23.5 cm (W) * 25.2 cm (H), internal size: 18 cm (W) * 19 cm (H), opening size: 19.6 cm (W) * 21.1 cm (H),suitable for installation on doors,thin metal doors and walls,cat doors are suitable for walls with a thickness of 6 cm.If the wall exceeds this thickness,there will be gaps in the cat door.Suitable for cats weighing less than 17 pounds (approximately 7.7 kg) and waist circumference less than 23 inches (approximately 58.4 cm).4 Way lock: The cat door with lock has 4 switch modes. The cat door can be adjusted by the red and green switches with labels. It can be set to open, only outside or completely locked, easy to adjust, and convenient for your pet to enter and exit.Cat flip cover: the transparent flip cover that most pets like, windshield and wiper-proof sealed flip cover with closure. The brush bar reduces energy loss and silent action, ensuring that pets and owners will not be disturbed.Easy to install: complete instructions are included, allowing you to easily install on windows, doors, cabinets, etc.Quality assurance: It is made of ABS plastic, resistant to weathering, and the surface is smooth and durable. 4 Way Locking Cat Flap: No in & No out( Fully locked) Free in & Out( Fully open) In only Out only Function Instruction of the Switches: 1.Turn Red and Green switches to both sides, pet is prevented from entering or exiting house. 2.Turn Red and Green swithes to right side, pet is allowed to enter house, but prevent from exiting house. 3.Turn Red and Green switches to left side, pet is allowed to exit house but prevent from entering house. 4.Turn Red and Green switches to middle, pet can leave and exit any time. Package Includes of TODARRUN Large Cat Flap Door : 1 X Large Cat flap door 8 X Screws 8 X Screw caps 1 X Installation instructions Note: There are total 8pcs screws, 4pcs used on the front and the rest used on back. Cut depth if necessary: If the cat flap door is too thick for the door you want to be fixed to, use a scissors, saw or cutting machine to cut along the line A or B as shown. The cutting scale is around 3 to 6 mm. For small cat flap door, the cutting scale is around 1 to 3 mm.