Hundreds of abrasive "balls" mounted on a flexible shaft - the fastest, easiest way we've come across to clean and polish older barrels or put a mirror polish in new ones. For used barrels, the Medium-Coarse hone, followed by the Fine, removes rough and tight spots and brings the bore to a bright finish that you can see and feel . . . just run a patch through it before and after; the difference is amazing! We found too, that we could feel tight spots during honing and spend extra time on them until they were evened out. On new barrels, the Fine hone by itself will bring the factory finish up to a beautiful, mirror-bright finish that's a real customer pleaser. Easy to use: chuck in a variable speed electric drill; wet the hone with Flex Hone^® oil; start the drill and insert the hone into the barrel from the breech end (if possible). As it cuts, a slurry of abrasive and oil develops to help speed the cutting action.