This pet door is great for applications where putting a pet door in an entry door is not practical. Our wall entry door can be used in a number of different wall materials including all types of siding, stucco, and brick. The Telescoping Tunnel allows for installation into walls 4.75" to 7.25" thick (extension kit, sold separately, will allow to extend beyond 7.25" thick). Double Flap system insulates for energy efficiency. Includes a non-rusting locking closing panel. Easy do-it-yourself kit complete with instructions.