WE HAVE TO MAKE OUR LARGE HOUSES WITH A FLAT TOP OTHERWISE THEY WOULD BE TOO LARGE TO SHIP UPS GROUND. Add this option to a house and the outside dimensions will increase to 21"x21"x23" on the inside dimensions increase to 16"x17"x14"h. BUT IT WILL HAVE A FLATOP RATHER THAN A PEAKED ROOF. THE LARGE HOUSE STILL HAS THE STANDARD 6" DOOR(WOOD FRAME & VINYL FLAP UNLESS YOU UPGRADE. THIS OPTION CAN BE APPLIED TO Basic, Deluxe, Heated, Cedar, and Ultimate houses but not Econo, Pods, Multi-level or Tree Stump houses. MAKE IT LARGE flatop$39.00 Please note that some of the houses pictured through out this sight have various upgrades and add-ons,most of the houses do not come with a window unless you add it and the standard door is made of wood with a vinyl flap.Unless stated otherwise in the description. DON'T WAIT FOR COLD WEATHER TO ORDER YOUR CAT HOUSE, CATS NEED PLENTY OF TIME TO GET USE TO THE IDEA OF USING A NEW HOUSE. ITEMS CAN NOT BE PICKUP UP MUST BE SHIPPED.