The lightweight Eco-Steel Air-Cooled Chimney was created so each flue section connects securely using a locking-tab design — ensuring immediate, tight assembly. With a 12 5/8” inner diameter and 15 5/8” outer diameter, it is rated for any solid fuel Isokern fireplace. This versatile system has been tested and approved for use with Isokern Standard and Magnum fireplaces in typical or Fire-Lite applications. CERTIFICATION : UL Listing No. MH8251 Tested to UL103/ULC-S604