What are the PlexiDor opening dimensions? The opening for the pet is smaller than the overall door size, because of the frame. Please see the following: Pet Door Size Opening for pet Small 6 1/2″ x 7 1/4″ Medium 9″ x 12″ Large 11 3/4″ x 16″ Extra Large 15 3/4″ x 23 5/8″ Electronic 12 5/8″ x 19 5/8″ The below size chart shows installation cut hole, opening for pet, and overall size, click on it to get the full size version. Note that there are two different installation cut holes for wall installation. This is because the tunnel is sloped, to ensure rainwater and similar will remain outside.