Though small dogs can use cat doors, these doors are designed specifically for cats. Cat doors are designed with wider frames and hard, see-through flaps.
Cats like being able to see where they’re going, so transparent flaps make them feel safer using the door. Soft door flaps drag along your cat’s back when she’s going through the door. Hard flaps are easier for cats to push through and don’t touch their backs as much. Cats also have proportionally wider bodies than dogs. Standard pet doors tend to be tall and narrow, while cat doors are wider and more square.