RCBS Competition Dies are meant for reloading bottleneck style cartridges for competitive marksmen who measure success in fractions of a millimeter. This two-die set's Full-Length Sizer takes cases to SAAMI minimums. It features a raised expander ball to allow extra leverage for smooth, effortless neck expansion (.204 and .25 do not feature a raised expander ball). The Seater Die doesn't crimp; it features a micrometer for super accurate bullet seating depth in increments of 0.001 inch, as well as a bullet loading window and a seating guide that ensures correct bullet alignment before and after seating. Note: Not for use with progressive reloading presses; competition dies do not require neck bushings.