The Superior unique, clean burning design provides 99% heating efficiency, allowing you to operate the logs vent-free with the fireplace damper closed. With no venting required, there is no heat loss up the chimney. Plus heating with Superior gas logs means you will never again be left in the cold with wet logs or without heat during a power outage. Specifications: 24" - 29,000 BTUs 30" - 35,000 BTUs 36" - 40,000 BTUs Minimum Fireplace Dimensions: 24" - 36FW x 28H x 15.5D 30" - 42FW x 28H x 15.5D 36" - 48FW x 28H x 15.5D