NOTE: Use this sturdy plastic brush to clean TOP-Flex & TOP-Rigid stainless steel liners, insulated metal lined chimneys, or metal stovepipe. The polypropylene bristles are acid resistant to coal, gas & oil flues; and will not scratch the stainless liners or black stovepipe. It's 1/4" threading allows for easy connection to the Fiberglass Rods.