Square wire chimney 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, and a brush that results in a more thorough cleaning with less effort. 1/4 NPT; all extention rods we stock from this manufacturer should fit except ones for pellet stove brushes.