The PetSafe Interior 2-Way Locking Cat Door is a door just her size. Give your cat unlimited access to her personal spaces (like her litter box and food) even while the human door is closed to keep odors (and the dog and kids) out. The transparent flap allows your cat to see her litter box on the other side of the door, making training and acclimation stress-free. As an easy DIY installation project, this cat flap fits any interior wood, storm, PVC, paneled or metal doors 1/2 - 2 inches thick. The flap opening is 5 3/4 x 5 3/4 inches and is designed for cats and dogs up to 15 pounds. PetSafe brand is here to help you and your pet live happy together.