If you want the highest level of precision and control, this Burstfire Primer Pocket Go & No Go Gauge Set is it. But keep in mind there are variations from brand to brand, and lot to lot. Cup thickness is a factor in if it will fit or how easily it will fit as well. Never guess again if your primer pockets were properly reamed or swaged. Enlarged body, curved (go gauge) / Swirl (no-go) design for a secure grip to be held by hand. It can also be attached to an existing industry standard 8/32 threaded hand tool handle, to maximize comfort. No-Go Gauges are made .005 over max pocket dimensions. If the No-Go Gauge can be inserted, it indicates your primer pocket may be too loose for some primers. It is strongly recommended at that point to either recondition your pockets, or discard/recycle the case. At times, the No-Go Gauge may be partially inserted into the primer pockets. That is NOT an indication of a loose primer pocket. It has to be fully inserted, without any resistance.