Lymance Dampers mount easily atop a flue tile with included silicone sealant. The included 32ft stainless cable drops down the flue and mounts in the firebox. The Power Lever is an important feature of this product. A firm tug on the cable drives a piston upward applying a whopping 143 pounds of leverage so the damper always opens easily. Instructions hardware and silicone sealant are included. Size 9in x 13in fits inside flue sizes 6.25in x 11in to 8.125in x 12.125in.