We have three cats -- 9 lbs, 15 lbs and 17 lbs -- and all of them use this pet door with absolutely NO problems. The door is translucent, so the cats can kinda see what's on the other side before going back and forth. The door itself, and the flap, are made of a very sturdy plastic, and the hinge action is smooth and simple. This door is very basic, and I think that's what makes it so great. Basically just two pieces to assemble, so there are no components that can break, fail or malfunction. I have used many pet doors throughout the years, and this is by far the best and most reliable.