Ideal Pet Door Deluxe White Dog Door Xx-Large Pet doors save you the trouble of constantly getting up to let your dog in or out. Give your pet the freedom to go outside whenever they want. Helps to prevent accidents. Xx-Large Deluxe White Dog Door Tamper proof mounting, door can't be removed from outside. 15 X 20 Opening Allows a pet with 15 shoulders to use this door. Inner telescoping frame that adapts to doors of 1/2 to 1 3/4 thickness High quality aluminum construction Dogs Up To 200Lbs Tamper Proof Yes Thermo-Insulated Yes Clear flap allows pet to see if slide isn't in place. Wall Installation Use Wall Kit # Wkdsl Door Sizes And Pet Weight If Your Cat Is Smaller Than About 15 Lbs Or Your Dog Smaller Than About 8 Lbs, A Flap Size Of Around 5 X 7 . If Your Dog Is Between 8 Lbs And 35 Lbs Consider A Flap Size Around 8 X 11 . If Your Dog Is Between 35 Lbs And 80 Lbs Consider A Flap Size Around 10 X 15 . If Your Dog Is Over 80 Lbs Consider A Flap Size Of 15 X 20 . Exact Measurement 1. Measure Your Pets Width Simply Open A Door The Minimum Width Needed For The Widest Part Of Your Pet To Comfortably Walk Through, Then Measure The Door Opening And Add An Inch. You Can Also Stand Above Your Pet And Use A Ruler To Measure The Widest Portion Of Your Pet, Then Add An Inch. It Is Important To Add An Inch Or So, That Way Your Pet Will Not Rub On The Door As You Pet Passes Through. 2. Determine Your Pets Height Measure From The Top Of Your Dogs Shoulders To Dogs Belly Or Chest Add 2 This item ships from a separate warehouse and may require extra time for delivery.