Paris Tack's 1200D Horse Hay Bag with Mesh Ventilation Flaps have revolutionized the hay bag market. Traditional hay bags are fully enclosed and can cause problems with moisture, which is potentially harmful to your animals. Our revolutionary design features 2 mesh ventilation windows around the bag to combat this problem. These vents are made of a reinforced mesh that is covered in a 1200D nylon flap. This covering still allows fresh air to enter the bag while protecting the hay inside. This exclusive design also prevents anything from entering your hay bag and spoiling your hay. This, combined with our ultra-tough 1200D nylon shell and reinforced seams result in a hay bag that is built horse tough and designed to last.