LEE PRECISION SMALL & LARGE PRIMER POCKET GAUGE SET Small and Large gauges to assure your brass meets the demanding SAAMIA(R) specifications for primer pocket dimensions. Insert the "GO" plug gauge into primer pocket, if it does not enter, the crimp must be removed. Consider using a Lee Ram Swage or Lee APP Swage to complete this task. If the "GO" gauge fits very loosely, reverse and verify with the "NO-GO" end. If the "NO-GO" enters to the bottom of the primer pocket, the primer pocket is oversized and will not reliably retain all primers. Mfg: Lee Precision