Use a DuraPlus 8 in. Diameter Elbow Strap to prevent excessive weight on the elbows by supporting the weight of the chimney. An elbow strap, like this one, is required to be installed between two elbows in offset installations. Multiple elbow straps may be required for offset installations. with its unique blend of materials, this 8 in. elbow strap is an easy to install, hard-working standby that anyone can use and prosper with!