The Hobie Mast Wind Direction Vane is a wind direction indicator that you mount onto the top of your Hobie Adventure Island or Tandem Island mast head. This indicator can be installed on all vintages of Hobie Islands. The indicator lets you know how to best properly adjust your sail trim or heading for optimum sailing performance. The vane slips over the head of your mast and tightens into place with a thumb screw. The indicator cannot be at the same time as the Hobie spinnaker kit (spinnaker kit has its own wind indicator).