Medium Breed Locking Pet Door - 11" x 9" Opening with Hard Plastic Flap by Weebo Pets Give your dog or cat the freedom to come and go as they please! Then, slide in the locking piece to keep unwanted critters out Keep your house warm & heating bills low: Weather-proof hard plastic flap with stiff bristles and gentle magnet closure creates a better seal than flexible flaps The opening is approximately 11" tall and 9" wide, which is perfect for a variety of breeds up to 40 pounds: terriers, spaniels, poodles, beagles, even cats (Consult our sizing chart if unsure) Adjusts to fit your door: Suitable for both solid and hollow doors of various widths, just trim the included plastic lining to cover any gaps in hollow doors Full assembly and installation instructions included; low maintenance and very easy to clean