Review on Aluminum Dog Door for Extreme Weather Conditions by Susan Rolfs

Seller information says "expansion tunnel". The carbide tunnel is only designed for an 8" thick wall, four sections of the tunnel are 8.5" wide. This is the only wall door I'm aware of that doesn't easily adjust to different thicknesses. There is nothing about it on their website or in the installation instructions. The instructions only apply to the unit installed through the door. I called support and they didn't offer any answers or further instructions. The only way to reduce this is to cut through the metal sections, good luck. If you have the right saw and decide to adjust it, measure the wall thickness and add 1/2 inch. The extra 1/2 inch allows the box to fit inside the outer entry panels. You might want to consider buying the door entry option and getting a 3/16"x12"x24" sheet of plastic for about $12 on ebay for your tunnel, it's a lot easier to cut. Easier to install and net savings in horsepower The Extreme Dog Door is still the best dog door for the money.