Chimney Wall Strap Band 8" Adjustable Wall Strap. Use on interior or exterior installations to support and stabilize the chimney By GSW SuperChimney Twenty-One A big company which makes a lot of chimney, so 6" and 8" are immediately available. Good products, competitive pricing. Their Chimney Twenty-One has a wall thickness of 1". Their Chimney 2100 (primarily for the Canadian market) has a wall thickness of 2".