Otis Bore Brushes have a proprietary Tufcor core wire that is corrosive-resistant and has a tighter twist for better bristle retention with twice the fill of other brushes with bristles right to the end. Caliber-specific brushes have the size indicated on the stem. Cleans .22-.45 Caliber. Includes: .22 x 2/.25/.27/.30 x 2/.35/.38/.40/.45 caliber nylon brushes.