The Endura double flap wall dog door is an excellent performer. Endura flaps are very weather tight. They are insulated and hollow and use full length magnet strips which are attached to bellows or accordion sections down the sides of the flaps. Endura Flap doggy doors also have magnets across the bottom of the flap, and a floating magnet bar in the frame. When the flap closes the three sides automatically adjust; if the flap expands in hot weather or shrinks in cold weather, the bellows on the sides adjust. The magnet bar jumps up to hit the bottom of the flap as well. This gives a very good seal, and makes the flaps very windproof. The manufacturer says that the medium double flap pet door will withstand a 50 mph wind without blowing open! These flaps are also extremely durable. They were tested with a machine that pushed the flaps open in both directions until failure occurred, and that didn't happen until after more than 3,000,000 cycles.
Endura flap dog doors for walls fit walls up to 7 ½ inches thick. The tunnel comes disassembled, which makes it easier to cut to the depth of the wall. Once cut the tunnel is assembled and the frames attached. The interior and exterior frames are identical on the double flap Endura, so you have the option of putting the locking cover on the inside or outside frame. This door is available in white, tan, or bronze (very dark brown).