A nylon bore brush in .20 size with an English Parker Hale thread, made to fit a .177 cleaning rod. Nylon bristles loosen powder fouling, carbon and dirt from the bore while being gentle on the barrel, which makes a nylon brush a good choice for regular cleaning and for use with solvents that can attack bronze. Screw it onto a cleaning rod with a matching thread, wet it with a little bore solvent and run it through the barrel a few times, then follow with patches or a mop to remove the loosened residue.