These are CCI #500 Small Pistol Primers. These are the "bread-and-butter" of reloading, the most commonly called-for primers in reloading recipes. CCI standard primers are remarkably clean-burning, leaving primer pockets cleaner and extending the time between pocket cleaning. That's a huge benefit for progressive reloaders. They are more sensitive and easier to seat than older CCI primers, and engineered for smooth feeding in automated equipment.