Product Description External size (L x W x H): 19 x 21.5 x 5.5 cm Internal size (L x W x H): 16 x 15.7 x 5, 5 cm It is suitable for cats weighing less than 7 kg and a waist circumference of less than 40 cm. Note: 1). Make sure the width and height (at the shoulders) of the animal are less than the scope of the animal screen, thank you. 2) The magnet at the bottom of the door frame is for aligning the flap after the movements, it does not work as a lock, thanks. Product upgraded features: 1. Convenient button-style switch, you can easily control your chat or other chat entry or exit options, only entry, entry, entry and exit, totally locked 2. Fixed groove with snap tabs for weatherproof brush strip greatly helps fix it. 3. The depth of the tunnel can be reduced, plus 1 pack of long + 1 pack of short screws, double-sided adhesive tape, to meet your needs, which install in various types of interior doors, exterior doors, walls, windows, cupboards, glass, etc. Installation instructions 1. Trace the outline on the door Draw the frame for the cat door on cardboard and cut it out. Use a pencil drawing around the edge of the cut paper on the door you want to be attached to. Note: 1. You'd better prepare these necessary tools first: pencil, cutter, electric saw, drill, screwdriver, double-sided tape. 2. If you can directly draw the outline of the outer door frame with the product itself, it is fine. 2. Cut a tunnel hole First drill 4 corners for the deep holes with an electric drill, then cut the tunnel hole with an electric saw starting with the drilled holes. Note: Generally, the average installation height is about 10-15 cm from the floor. 3. Reduce the depth of the tunnel if necessary If the cat door is too thick for your door, use scissors or a cutting machine to cut part of the tunnel along line A or B. The cutting scale is approx. 2-4CM. 4. Wrap the tunnel hole Once the tunnel has been dug, it is best to wrap it with a layer of wood skin. 5. mount the door Mount the cat door with double sided tape on the door. 8 screws have been provided for your use, tighten them with a screwdriver on both sides. Note: 8 screws for 4 holes on both sides, screw them all in the 2 sides as above picture, please. These 8 screws are designed to work together, they are not short. 6. Done Place the screw caps on the screw holes, press them down. The installation is completely finished.