These corrosion resistant bronze brushes meet or exceed military specifications and are designed to satisfy shooters who want the best tools to maintain their firearms. Best Bore Brushes will not scratch or harm the bore in any way. Each brush contains the maximum number of bristles, and because of their density, Tipton recommends that these brushes be used only with a quality 1-piece rod and with an appropriate bore guide.Includes brushes for 17, 22, 243, 25, 6.5mm, 270, 7mm, 30, 8mm, 338, 375, 416 and 45 calibers. All brushes have standard 8 x 32 male threads except the 17 caliber brush which has 5 x 40 male threads. Packaged in a durable, hinged plastic box with marked slots.