The Sinclair Micrometer Top allows the handloader to convert existing L.E. Wilson seaters to micrometer seaters. The top is constructed of stainless steel and is graduated in increments of .001 inch. To use, remove the existing seating stem from your L.E. Wilson Seater cap, and install in the Sinclair Micrometer Top. Now you are ready to make quick and easy changes to your cartridge's overall length. The top utilizes your existing seater stem or you can purchase an additional stem. Stem is not included.