Max two "45 degree bendsno need cut the bristle short. Our chimney brush can be directly used to clean through 170mm. Below please find more details FYI :
1/ This chimney brush is designed for sweeping chimney/duct ( either bricks, clay, masonry, stone or steel material;and the chimney shapes do not matter, round, rectangular, or triangle etc.) and without soft lining (the nylon bristle have sharp edge, may scratch the soft lining.
By vevor