Rectangular wire brushes are a compact, low profile design. The benefits of this design are a brush that follows chimney and flue contours, a brush that will easily reverse direction in the flue for easier cleaning, a brush that will easily negotiate angles and bends up to 90 deg., and a brush that results in a more thorough cleaning with less effort. 1/4 NPT; all extension rods we stock from this manufacturer should fit (except ones for pellet stove brushes).