Eliminate musty odors under boat covers.Mildew gas bags protect against mildew and eliminate musty odors under boat covers. No formaldehyde is used in the bags and they are safe for the environment, humans, and pets. The bags are placed in a clear plastic clamshell which is then placed on a flat surface in a central location or if you want it hung,Key FeaturesProtect against mildew and eliminate musty odorsNo formaldehyde is used in the bagsSafe for the environmentEliminate musty mildew under boat covers, equipment