Air Flow Tell Tails Red Green all you to trim your sails for optimum performance. Attached air flow over sails is critical. Air flow directions are indicated by these tell tails. Made of light weight rip stop nylon (Red / Green). Attaches to sails with waterproof adhesive disks. SAIL POWER: Watch the sail, pay close attention to the trim or adjustment of the sail. When the front of the sail, just behind the mast, luffs or flutters in the breeze, you lose power. To start moving, pull the sail in just enough to stop the sail from luffing or turn the boat away from the direction the wind is coming from. There are also short ribbons hanging on either side of the sail called “tell tails”. The tell tails react to air flowing over the sail and will help you see that the sail is pulled in too tight or too loosely. If you pull the sail too tight you will stall the sail power. The tell tail on the back side of the sail will drop or do circles. Ease the sail out until it luffs, then pull it in just a little until it stops luffing. You will adjust the trim whenever the wind changes direction or you change course.