This unit will convert your one at a time priming to a tube fed priming system and also eliminate the handling of primers. The RC Supreme Auto Prime body attaches to the same place as the standard priming arm. Attach the proper primer cup and seat plug to the priming arm slide, insert the correct primer tube and safety shield, fill the primer tube and you are ready to prime. The straight push-pull primer arm slide reduces the chances of primers falling out of the primer seat plug. 100 primer capacity. Large and small primer pick up, feed tubes and primer seat plugs included. RCBS lifetime warranty.