The PERKO Base Mount Red All Round Navigation Light is certified for use on sail or power driven vessels under 20 meters (65 1/2 feet) in length. Black Plastic12, 24 or 32 Volt Bulbs IncludedCertified for use on Sail or Power Driven Vessels Under 20 Meters (65 1/2 feet) in Length Screw Size: #10Height Overall: 4-7/8"Height Lens: 2-3/4"O.D. Base Inches: 3-5/16"