USCG certified for use on sail or power driven vessels under 20 meters (65.6 ft.) in length. 3-mile visibility. Black plastic and chrome plated zinc alloy top, and chrome plated zinc alloy mounting bracket with waterproof cover. Stowaway plug-in type with 3/4" diameter anodized aluminum tube w/gold plated contacts. Plastic adapters for flat or "V" type 45° windshields. Clear lenses. 12V bulbs included. Screw size is 8.