The 4-brush kit includes an upper receiver brush, bolt carrier brush, chamber brush and .308 Bore brush. The 2-brush kits contain two of the selected brush type. Please use the drop-down menu to select your preferred options. These brushes are manufactured to close tolerances for precision cleaning. Constructed from a distinctive blue fiber, they are thick, stiff and maintain their shape effectively. This design facilitates back-and-forth motion, unlike traditional brass and bronze brushes. The brushes can be used multiple times before showing signs of wear. For comprehensive cleaning, use them with Iosso bore cleaner and triple action oil.