The Control Cover is adjustable. You can open it partially or almost straight up, depending on how well your chimney draws. This saves you energy over a regular damper system which can only be either open all the way, or be shut. See U.S. Department of Energy study results. br Website: br Address: 2940 East 4430 South, Salt Lake City, UT, 84124, USA. br Phone: 801-273-1800 br Email: controlcover@juno.