Comfort Flame's Anti-Draft Shield is designed for use with 8 diameter round top terminations only RTL, RTTL . Features galvanized steel construction and should be used with FMI wood burning fireplaces only. All Direct Vent and Wood Burning products require venting to the outside of the home to achieve proper ventilation and firebox combustion. FMI Products offers a full assortment of venting components to properly vent the Direct Vent or Wood Burning fireplace. Features For use with FMI wood burning fireplaces only. Galvanized steel construction. For use with RTL or RTTL terminations only. 8 inner diameter and 12 3/8 outer diameter. Made in the USA. Specifications Overall Dimensions 21 W x 21 D x 27 H .