USCG certified for use on power driven vessels under 20 meters (65.6 ft.) in length. 2-mile visibility. Black plastic top, chrome plated zinc alloy base 3/4" diameter anodized tube with locking collar, and 16 degree rake. Screw size is #8. 12V bulb 0337011DP included. Telescoping base (3-3/4" x 1-5/8") included. Spare Base #1059T00DP.