Uses:Stainless Steel Chimney Flue Cowl Pipe Rain Cover Protector Cap Ending.Rigid design and reliable mounting method ensures that the cap is as durable and aesthetic as a Chimney cap. SIMPLE INSTALLATION:makes it a good solution for all Chimney pipe endings.Hoop design,lengthened screw can be adjusted, effectively solving the problem of dimensional error Chimney Cowl CAP:This Chimney cap made up of 304 stainless steel, will not rust, fall off or break and easy to clean.(note the size is the inner diameter of the interface) IMPROVES COMBUSTION : by not allowing the fumes go too fast out of the Chimney this flue cover creates an even combustion of the burning material thus not only saving you money and fuel but also keeping the warmth longer inside.