Gear Locker, (1) Tier, (1) Wide, Steel, Gray, Powder Coated Finish, 18 in W, 36 in D, 90 in HMfr #: ILKS18247201AADRW To determine what skylight you need, measure the size of the rough hole opening in your roof. Skylights sit directly on your RV roof. If necessary an inner garnish is available to finish the inside hole. No metal flange is used with these single pane skylights. Use a skylight size that is equal to or greater than your hole dimensions. Always use included sealant. Note: Inners must be the size as the hole you are working with.