Medium, White, Pet Door, Solid Aluminum Construction, Locking Panel, Transparent Single Flap For Weather Tight Seal, Easy Do It Yourself Installation, Fits Doors From 3/8" To 2" Thick, Flap Opening Dimensions: 8-1/8" x 11-3/4", Cut Out Size: 8-7/8"W x 13-3/4"3/4"H, Great For Pets Up To 40 LBS.