The Ideal Thru-the-Wall Pet Door is intended for wall installation and fits walls from 4-1/4 in. to 9-1/4 in. thick, offering flexibility for a wide range of home constructions. The double-flap design creates an air pocket between the flaps within the pet door, which creates a barrier to help reduce heat transfer. This allows dogs dependable access in and out of the home. Installation is designed to be approachable for homeowners, with clear instructions included to support proper setup. To choose the correct size, measure your pet across the widest part of their body and confirm their weight. If your pet is near the upper end of a size range, selecting the next size up can improve comfort and usability.