Our custom premium grill covers are designed with our specially engineered Inner flow ventilation systems, and come in a variety of sizes so that they can fit on most grills on the market. The Inner flow system is molded from a highly durable PVC material that is attached to our grill covers. This specially engineered section allows air to move freely throughout the covered barbecue, yet prevents rain and snow from entering, keeping your grill dry and free of damaging condensation. This keeps your grill in commission for longer than any other product on the market, and because they are built with the highest quality materials. Montana Grills barbecuecovers are flame retardant, resistant to UV radiation, don't crack in the cold, and are mildew and fungus free.