You will find that the brushes produced by OTIS will give you many times the life of most brushes. Each 2 pack contains one bronze and one nylon bore brush. Our caliber-specific brushes are color-coded and have the size indicated on the stem, ensuring you grab the right brush every time. Otis brushes have a proprietary Tufcor® core wire that is corrosive-resistant and has a tighter twist for better bristle retention and brush life - plus twice the fill of other brushes with bristles right to the end.