The 15" (38.1cm) vane can be through bolted or tapped into the masthead. The mounting socket has a 5/16"?18 thread. The entire unit weighs only 3.9 ounces (111 g). Features spike above vane to keep birds off your mast. Sapphire suspension system and reflector tabs on the bottom surfaces make WindTrak 15 highly sensitive and visible even at night! Description 15" WindTrak vane