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: .17HMR/ .177 WSM, .177 calLength: 1 InchThread: 5-40Includes: 1 Bronze BrushOur caliber-specific brushes have the size indicated on the stem, ensuring you grab the right brush every time.