Bronze or nylon bristles wound on twisted brass wire and looped to prevent scratching. .17 Caliber for .177 caliber airguns and .17 caliber rimfire and centerfire guns. .20 Caliber .204 Ruger and .20 caliber wildcats. Fits Dewey and Outers small caliber rods. Mfg: Dewey SPECS: 2½" (6.3cm) long, 5-40 male thread.