Petsone&reg; Ideal Pet Door for Screen Pet Gates for Cats and Dogs Quick and easy installation, for screen doors and windows, you need use glue to fix it, and glass cement is recommended. Fits all door and window screens, Suitable for all pets up to small/large size cats and dogs Doors close automatically, great for home and cottage Make sure that the width and the height (shoulder level) of the animal are inferior to the pet door. Large outer size: 18 x 14(L x W); Small inner size: 16 x 12(L x W)