The choice for most sailors worldwide. The 15" vane can be through bolted or tapped into the masthead. The mounting socket has a 5/16"-18 thread. The entire unit weighs only 3.6 ounces (101g) Sapphire suspension system and reflector tabs on the bottom surfaces make Windex 15 highly sensitive and visable, even at night! Can be equipped with windex light #3200.