PlexiDor Pet Doors do not require costly vinyl replacement flaps. The unique saloon style, shatter resistant dual thermo-pane, hardened acrylic panels open and close with a gentle push and automatically close without banging. Each panel is lined around all four edges with snug fitting, high density, industrial nylon pile weather seal to provide superior draft-control. When closed, the panels reduce air conditioning and heat loss. PlexiDor Wall Units can be installed into stud, brick, block or cement exterior walls up to 12 inches thick. Each wall unit includes an aluminum tunnel that connects the interior and exterior frame. The tunnel materials ensure a professional fit and finish that provides a quality appearance.