Tell me more about the PlexiDor cat door! The PlexiDor cat door is intended for cats up to 24 lbs and dogs up to 9 lbs. The weight limit for cats is so much higher because they’re built differently than dogs and move differently than dogs. A 24 lbs dog needs much more space than a 24 lbs cat. If you have a dog over 9 lbs, check if they can pass through an opening that is 6 1/2 x 7 1/4 inches through cutting a hole that size in a piece of cardboard and enticing the dog to go through. If it doesn’t seem comfortable with the space, go up to a medium size PlexiDor. The door is available for installation through a house door or a wall, or can be installed with a glass kit. The sturdy aluminum frame is available in white, bronze, or brushed aluminum. The PlexiDor cat door is different than the other sizes: It has a single-pane design instead of saloon style doors It doesn’t come with a security plate – the opening is too small for anyone to get through It has a different lock than the larger doors The larger PlexiDor models come with a lock and key. The small door has a lock that allows some different settings. It can be: Open Locked Open in one direction only, that is, allow your pets to come in, but not go out again. Or, allow them to go out but not come back in.