Derby Originals is the original inventor of the 4-sided hay bag U.S. Patent No. D742 078. Our four-sided hay bags are the only bags on the market that allow your horse to freely eat from any part of the hay bag. These patented hay bags are the result of years of careful study and testing to create a design that is attractive functional durable high-quality and preferred by horses. Our bags are constructed of reinforced nylon webbing that is stronger and more durable than any mesh or fabric hay bag. These bags are designed with cross stitches at every intersection and bartack stitching at all stress points along the top sides and bottom of the bag. This hay bag also features a reinforced fabric bottom that is covered with nylon webbing. Our bags are built tough from premium materials and are designed to last for years to come. This hay bag is designed to be a great everyday feeder for most horses and other animals: it measures 13 x13 x26 and can hold about 2-3 flakes of hay. This hay bag has 3.5 x1.5 rectangular openings which will prevent hay wastage and slow down their rate of consumption but still allow for frustration-free feeding. This premium hay bag also includes a 6-month limited manufacturer s warranty offered by Derby Originals.