Custom E-Class EF Series Skywindow - Rough Opening: 18-1/2" x 68-3/4", Daylight Area: 17-1/8" x 67-1/2", Daylight Opening Square Ft: 6.61' - Skylight for use with thin roofing materials such as composition, slate, wood shingles and shakes up to 3/4" thick - Minimum Roof Pitch: 3" in 12" - For deck mount applications - Not for vertical applications