Class A Customs 19 x 22 od Trailer New Skylight Plastic Lexan Polycarbonate rv 15 x 18 ID CLEAR NO SHIPPING TO ALASKA, HAWAII, PUERTO RICO, or USVI. Color: Clear Mounting Flange Is Pre-drilled For Easy Mounting Inner Dome Dimensions (this is roughly the size of the hole you will need in your unit): 15" wide X 18" long Exterior Dimensions: 18 1/2" wide X 21 1/2" long x 5" tall