This CRL Screen-Fit Pet Door is ideal for mounting on window or door screens for small pets up to 20 pounds (9 kg). The plastic snap together gray frame is ideal for mounting on basic screen cloth 2" (51 mm) away from the frame. Installation is simple, simply lay one section of the door frame on a flat surface, then position the screen over the door frame. Position the flap, and lay the top part of the frame over the bottom. Use a soft mallet to snap the two frame pieces together, then open the flap and using a utility knife cut the inner screen cloth away. Flap size is 9" X 11" (229 X 279 mm). Flap is held in the closed position by a magnet.