Redding uses only top of the line steel alloy to machine their dies. Redding 6.5 GAP 4S Neck Sizing Dies are guaranteed to return your brass to SAAMI standards. The Neck Sizing Dies are heat treated to ensure a perfect sizing every time on all quality brass. The 6.5 GAP 4S Neck dies have a neck expander and decapping rod built right in to perform all the steps to prep your cases for primer and powder and a bullet.