The Lyman Pro Micrometer Seating Die gives you exact bullet seating length and minimal run-out. The seating die has a micrometer adjustable seating head for precision bullet seating length. If you want to change your bullet seating depth a few thousandths of an inch, simply turn the micrometer head to the required setting. Its floating bullet seating punch centers the bullet on the case and eliminates excessive run-out. The Pro Micrometer Seating die is also made of corrosion resistant stainless steel which protects it from rust and keeps it looking like new for a lifetime of use.