I had searched for a long time, to find chemical-resistant small stoppers, to use for cleaning my vintage WWII rifles. Over the years, copper and other deposits had built up in the barrels from many years of inadequate cleaning. Regular cleaning, with bore brushes and patches, seldom removed enough deposits. One of the best ways to remove these deposits is to plug the barrels at the muzzles and fill them with solvent and ammonia, and allow them to soak, frequently for hours or days, and multiple times. Due to the small bores of the rifles, and varying sizes, it was very difficult finding stoppers small and pliable enough, variable in sizes, and chemical resistant, to serve this need. These stoppers, which I bought in several sizes, fit the bill to a tee. They are pliable enough to fit tightly and seal the muzzles, are reusable and totally resistant to the chemicals; and, each size can serve multiple rifle calibers.