This cat door solves the litter box location problem by hiding it behind a closed door! The purpose of Cat Hole & #153 is to hide kitty's litter box behind a closed inside door. It installs easily in a basement, laundry room or spare closet door. With the door closed, kitty can get to the litter box while dogs and toddlers are locked out. The messy litter box is also isolated from the home "living space" providing a much improved environment for the family and guests. Cat Hole & #153 has attractive arch frames that are made of furniture quality baltic birch. The wood frames can be painted or stained to match the owner's decor. This cat door also includes a removable brush that grooms kitty by collecting loose cat hair. The brush snaps in and out easily for cleaning. This cat door installs easily. Many of our customers also comment on this. Cat Hole & #153 comes with complete easy-to-follow instructions. Dimensions: You can fold a piece of paper into a 8.5" X 8.5" square. Place this at the bottom of your door & you will get a good idea of what Cat Hole & #153 will look like. Outside of Frames: 8.5" wide X 8.5" high Inside of Frames: 5.75" wide X 7.125" high Opening (with brush inserted): 5.0" wide X 6.75" high Note: Most cats, up to 20 pounds, will easily pass through the brush opening.