Windex 15 is the overwhelmingly popular choice for all cruising and racing boats 22' and bigger.Sapphire jewel bearings: Popular around the world because they offer such an exceptional value, these wind indicators are super-sensitive to slight changes in wind direction at the masthead. They feature sapphire jewel suspension bearings, large fin/low inertia vanes and easy-to-read, adjustable tacking-tab systems for quick reference.Day or night visibility: Reflector tape on the vane and tacking tabs make Windex 15 easy to see day and night.LED Light for Windex 15 and Sport (sold separately) illuminates reflective reference tabs on the Windex.Wind tunnel tested:They have been wind tunnel tested to wind speeds of 80 knots!Bird-proof spike: Bird-proof Windex 15 features a 10" stainless steel spire to prevent birds from landing on vane. The choice for most sailors, the Windex 15 incorporates a 15" vane and reflectors for high visibility day and night.Includes through-bolt or drill and tap mounting socket; 5/16"-18 stainless stud, washers and nut. Stands 12 3/4" tall and weighs just 3.6 ounces.