The Lee Auto Prime Hand Priming Tool is a great tool for the handloader wanting to prime each brass case by hand. The Lee Auto Prime utilizes special shellholders that will only fit the Auto Prime, they will not fit in a reloading press. There are twenty different shellholder sizes to suit the needs of all reloaders. Auto Prime Shellholder utilize the same number as Lee Universal Shellholders and will fit the same cartridges.