Custom Logo Industrial Heavy Duty Windsock State Flag Drainage Vents Windsocks are Drainage Vents Windsocks are equipped with a drainage vent at the bottom of the windsock to prevent build up of water and the eventual formation of mold within the windsock basket The three blue stars in the center represent the three states that were created from the Louisiana Purchase of 1803 Our 600D PU polyester is coated with water proof coating and achieved a hydrostatic pressure test result of 110 mbar when independently tested as per AATCC 127 2008 Our 600D PU polyester prevents premature fading and is characterized as having "Excellent UV Protection" when independently tested as per BS EN 13758 1:2001