The RCBS Case Neck Brush is designed to help reloaders clean dirt and powder residue from the inside of case necks while at the same time applying lubrication to ease the amount of force required during case neck expansion during the resizing process. Notes: For use with the RCBS accessory handle product# 477-820 (sold separately)Nylon bristlesBrush must have lube applied to the bristles to lubricate the inside of the case neck