Boxed Air Vent for Tuffy Windscreen The Aer-Flo boxed hemmed air vent is equipped with a flap that allows air to flow through your sports field windscreen to reduce stress and prevent damage to the windscreen. The border on the boxed window is reinforced with two layers of vinyl fabric for long-lasting durability. The BHV hemmed air vent measures 6"Hx12"W and is designed for use with Aer-Flo's Tuffy privacy windscreens.