RCBS Large Primer Pocket Uniformer is designed to ensure that primer pockets are cut to the correct SAAMI depth specifications, cleaning out built up carbon residue from previous firings and squaring the bottom of the primer pocket with respect to the case head. This step is important as variations in the seating depth of the primer can change how the firing pin strikes the primer producing inconsistent ignition. These are for use with the RCBS Case Prep Center Only.