Perfect Pet Multi-Flex Pet Door Maximum energy efficiency Inner telescoping frame that adapts to doors of 1" to 1 3/4" thickness Spring loaded locking slide for one-handed use Flap Sizes:Medium  6 5/8" by 11 1/4" andExtra Large  10 1/4" by 15 3/4" Need Assistance? E-mail Ideal Pet Products customer care specialists seven days a week! Need Assistance? E-mail Ideal Pet Products expert US-based customer care specialists seven days a week!