With modern sleeve/micrometer seating dies, all alignment and interaction should be between the shoulder/taper of the case and the die, so Area 419 designed a seating plate for the ZERO, meant to offer a perfectly flat surface to push your cases, with no possible die interference. This seating plate is precision ground stainless steel, guaranteed to be flat, and has more contact surface than any traditional shellholder could have. It also has no extraction rim, so there is no way for it to be making contact with the seating sleeve that should be actuated by the case itself – which is an easy way to induce runout in the seating process.
NOTES: This works ONLY with the ZERO Reloading Press. This also, by design, has no extraction rim. This may result in cases needing to be removed by hand from seating dies when the bullet is seated. Some will freely release from the seating die with gravity, others need to be removed by hand.