Pro Shot .223-Caliber/5.5mm Military Style Nylon Chamber Brush HD nylon bristles wont deteriorate when used with solvents or oils Heavy duty stiff nylon bristles with brass core and coupling that is wound through the brush coupling for added strength and durability Nylon Bristles resist ammonia and oil-based cleaners All Pro Shot brushes are Proudly made of USA components and assembled in the USA, #8-32 Threads Fits Standard American Cleaning Rod with #8-32 Threads