Purchase a Bullet Guide, Seater Plug and Shellholder (if necessary) to convert your RCBS Competition Seater Die to another caliber. Bullet Guide specific to bullet diameter. Seater Plug specific to bullet type. Shellholder or Extended Shellholder determines fit to specific cartridges.
These replacement parts are only for the newer "non-click" style RCBS Competition Seater Die. If you own an RCBS Competition Seater Die that clicks when you turn the micrometer you will have to purchase a new model die to use these conversion parts.