Forster Ultra Micrometer Seater Die 308 Winchester Die body is made of Polished Steel Micrometer top is made of Aluminum with a hard coat black anodizing making the graduations easier to Ultra (Micrometer) Seating Die The Ultra Seating die allows you to adjust the seating depth to .001"; or even .0005"; increments. If using Forster Dies in a Forster Co-Ax press shellholders are not required since Forster presses d