BoreSmith, Cal 40, 10, Pistol Bore Brush, Phos Bronze Our standard brush has phosphor bronze filaments, and it is made for pistol/revolver length chambers Standard 8-32 threaded connector is made of non-abrasive aluminum Carbon-steel twisted core wires give our brushes superior strength that resists bending Packed in heavy duty plastic tubes for safe and easy storage Phos bronze filaments clean with more friction than nylon filaments do