Otis brushes have a proprietary Tufcor core wire that is corrosive-resistant with a tighter twist for better bristle retention and brush life. With twice the fill of other brushes and bristles right to the end, you get superior quality and precision cleaning every time. Cleans: 6.8mm, .270cal, 7mm Length: 2in Thread: 8-32 Includes: 1 Nylon Brush/ 1 Bronze Brush