"Purchased this door with fairly low expectations and was pleasantly surprised! I have two shih-tzu/poodles that are 14&17lbs and was able to use the small door opening just fine. Took a couple days for one of my boys to get use to it but once he realized the freedom the door provides, he was zippin in and out of there. Another excellent thing is you don't need to worry about letting them in and out and have them scratching the door to let you know what they'd like to do. :)
The quality of the door is very good and the instructions are very straight forward. It was very easy to install and becareful to put screws in the door if you decide to securely place it there. Only reason for 4stars is because it doesn't come with holes or something to secure it there, i had to place holes in the door and the frame for it."