The secret is in the sapphire jewel suspension bearing, large fin-low inertia vane, and easy-to-read, fully adjustable tacking tab system. Windex is the perfect choice for all cruising and racing boats 15 feet (4.6 meters) and bigger. Reflector tape on the vane and tacking tabs make Windex 15 easy to see day and night. Windex vanes are sturdy and when installed properly, offer many years of use. They have been wind tunnel tested to wind speeds of 80 knots! Windex 15 has a 15" (38 cm) vane. Includes through-bolt or drill and tap mounting socket; 5/16" -18 stainless stud, washers and nut. Stands 12.75" (32 cm) tall and weighs just 3.6 ounces (101 g).