Conveniently packaged 13-piece caliber-specific set of Best Bore Brushes means you always have the right brush at hand. Contained in a durable, hinged box with marked cavities, it's easy to select the correct Best Bore Brush for your particular application. Because they are caliber-specific, you can be assured of an optimum fit to your firearm's bore for efficient and thorough cleaning. 17 to 45 caliber (does not include 20 caliber). All brushes have 8-32 threads (17caliber has 5-40 threads and is a standard bore brush.) See page 51 for the complete line of bronze and nylon Tipton Bore Brush Sets for handguns, rifles and shotguns.