The Pro-Shot Benchrest Quality Bore Brushes are high quality, brass core and bristle brushes. Each brush is sized to make cleaning faster & easier and aid in extended brush life. The brushes are designed for for competition shooters and are made to withstand frequent use. In fact, several world records have been set due to the cleaning of a bore with these brushes. Most importantly, the brushes will not harm the bore!FeaturesAll brass construction (bronze bristles and core)Standard #5-40 or #8-32 thread pattern availableSpecifically designed for each caliber