We carry a variety of sizes of poly tarps to cover your load. They are made of polyethylene and are 4 mil thick. They are a nice inexpensive option to protect your load of trees from wind damage. They don't offer much ventilation so they aren't great for long trips, but will do the trick if you are just transporting around town. These tarps also have grommets in the corners and along the side which make them easy to tie down.