Conveniently packaged 12-piece caliber-specific set of Ultra Jags means you always have the right jag at hand. Contained in a durable, hinged box with marked cavities, it's easy to select the correct Ultra Jag 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 jags have 8-32 threads (17caliber has 5-40 threads)..