Pet flap features an unbreakable Lexan flap and four way locks. You can choose from free access in or out, in but not out, out but not back in or completely locked in both directions. It also has a telescoping frame that insures the core of the door through which you mount is covered. Pet flap is also perfect for indoor cats so you can place their litter in a garage, basement or utility room. You can also place their food in a separate area away from hungry and curious dogs. Flap opening measures 7 1/2" x 10 1/2".