Poly shipping bags are fancy plastic bags designed to ship a variety of items: foods, produce, powders, ice, chemicals, waste, magazines, and other products.  The bags are composed of a film called polyethylene. There are several features and designs of these bags.  They can be gussetted in order to fit a larger amount of products, they can be made to stand up on their own, or they can be made to lie flat.  Some of them have handles cut in or added, and some of them have resealable openings for easy open and closing of the bag.  Some poly bags called boil-in-bags are designed to withstand the effects of heat so the enclosed food can be cooked right from the bag.