Icon Technologies's Skylight Inner Dome for a 23 7/8" x 16 1/4" Skylight opening. An Inner Dome provides a layer of insulation and reduces condensation forming on the outer skylight. • Molded of white ABS plastic material with a clear center insert. • Fits all standard 23 7/8" x 16 1/4" skylight openings. • Opening Dimension: 23 7/8" x 16 1/4" • Outer Dimension: 26 1/8" x 18 1/2" x 5 1/4" Finish off your replacement with an ICON skylight | Icon Technologies Skylight Inner Dome, for SL1826 in White | ABS Plastic