I am cleaning out my attic and found this item I purchased about 10 years ago.  I intended it for a Laser sailboat but it will fit smaller sailboats.  

Davis Windvane and C-Vane

This item has never been used.

Sensitive, reliable, lightweight with quick and easy and secure installation and removal.
Suitable for Mast Diameter Ø 50mm - Ø 63mm (Ø 2 - Ø 2.5 inches)