Perfect Pet Pet Door with Telescoping Frame Inner telescoping frame that adapts to doors of 1 -inch to 1 -inch thickness Impact-resistant super-strong thermoplastic Clear flap allows pet to see if slide is in place Tamper Proof Mounting System, door cant be removed from outside Simple 4-step installation (Average install time: 20 minutes) Flap Size 15-inch by 20-inch Manufacturer Warranty does not apply to product purchased through Amazon Warehouse Deals Need Assistance? E-mail Ideal Pet Products expert US-based customer care specialists seven days a week!