Installed like a standard window air-conditioning unit, this ingenious cat door allows your cat independent access to your home and yard without claw damage to screens or the need for you to constantly open and close a door. The box door fits single or double-hung vertical sliding windows 24" to 36" wide, and unlike traditional pet doors that have to be cut into a door or wall, this unit installs without renovations of any kind, and can be relocated at any time. Inside the box is a switchback corridor lined with a series of vinyl curtains allowing cats safe passage, and acting as an airlock baffle that minimizes heating or cooling loss and blocks wind. A manual door can be closed at your convenience to keep your cat inside at night. The entrances have a floor of weather-resistant carpeting that can be removed and washed, and the sturdy ABS plastic exterior withstands the elements for years of reliable use. Minor assembly. 9" H x 27 3/4" W x 23" D. (14 lbs.)