Another Ron Power "trick-of-the-trade". Use to adjust barrel/cylinder gap, square the rear barrel face and eliminate high spots. Four Sizes: .540", for Ruger Security Six, GP-100; S&W K; Colt Mk III, Official Police; Charter Arms; .560", for S&W L; .625", for S&W N; Ruger Blackhawk, Super Blackhawk; .687", for Ruger Redhawk. Mfg: Brownells
