Spirit is the color. The zipper setup is a modification of the standard sail, to allow for reefing. You un-zip the lower panel. You lower the main and tie off the halyard for a smaller sail to be used by kids or in high wind.

Unless you are light or sail in very high winds, I don't think you need it. The Wave is underpowered and comes alive as the wind increases. If high wind is an issue, I recommend the main traveler system.