The Plexidor can be installed in any type of house door, wood, steel, fiberglass, hollow core, etc. Door units frame out a door that is 1 3/4". Standard thickness of a door in the United States and Canada. The frame of the will protect your pet from the cut-out edges of the door. There is no need to 'frame out' the hole. If you have a French doors consult your local installer to see if they can use your French door or if you will need to install a different door slab. Doors have locks, plus separate security plates, and can only be unscrewed and removed from inside your home. Panels close automatically when pet has gone through. Mechanism concealed within main frame. See-through Plexiglas panels open smoothly both ways with a gentle push. Versatile twin panels need only light pressure to open them, so large and small pets can use the same door. Panels are molded to form a Thermo pane effect for insulation, and edged with snug fitting, high-density, nylon pile weather seal. Size extra large is a solid 3/8" thi Type: Doors Size: 13.75 x 15.5 Inches Color: Brown Color Mapping: Brown