The Plexidor PDWALLMDSV Silver Wall Mount Pet Door Unit - Medium can be installed into brick, block or cement exterior walls up to 12-inches thick. Using an aluminum tunnel which connects the interior and exterior frame, the Plexidor PDWALLMDSV will not rust and has no sharp edges to snag your pet. The Plexidor PDWALLMDSV uses unique, shatter resistant, dual thermo-pane Plexiglas panel that opens with a gentle push and automatically closes tight without banging. Using a snug-fitting high density nylon weather seal, the Plexidor PDWALLMDSV door panels are designed to provide superior draft-control, keeping heating and cooling in the house. The Plexidor PDWALLMDSV interior and exterior frames are made from heavy duty anodized aluminum that won"t rust, bend, crack or warp. Features: * Rigid, high-impact, insulated and shatter-resistant panels do not require costly vinyl replacement flaps and create a window for your pet * Panels open smoothly with gentle push and close automatically allowing large and small animals to use the door with ease * Designed for walls that measure up to 12-inches thick; Large unit will fit exactly between 16-inch on-center studs * Anodized aluminum interior and exterior frames won’t rust, crack, or warp * Perfect for animals that weigh up to 40 pounds * Keeps out unwanted guests with cylinder lock * Cut Hole of 11-7/8-inch wide x 15-1/4-inch high * Overall: 13-3/4-inch wide x 17-1/2-inch high * Opening of 9-inch wide x 12-inch high * Security with lock, key and steel security plate * No replacement flaps required * Highest energy efficiency What"s In The Box: * * Plexidor PDWALLMDSV Silver Interior and Exterior Frame * Aluminum Tunnel Pieces * Installation Instructions * Mounting Hardware * Steel Security Plate * Two Keys * Lock