If you're turning necks, or just checking them for wall thickness uniformitiy, a good tubing micrometer is essential. You can search for a used Mitutoyo on eBay (and hope that it's not broken), you can purchase the excellent Sinclair for $129, or you can get the great new Holland's product for $80.
The ball tip is just the right size for measuring 6nn cases. The micrometer is easy to adjust and is accurate to within .0001". The lower half of the "U" frame is plastic coated so you can clamp the Holland Mic into a vise, or just C-clamp it to a table edge. This makes it very handy to use.
The Sinclair unit comes with a built-in stand, which is a nice design, but with the Holland you have the choice of holding the unit in one hand or clamping it down. We like that. Sinclair makes a fine micrometer, but the Holland tool is a much better value. The Sinclair does have one clear advantage--the ball tip is mounted on the end of a narrow shaft. This allows you to measure wall thickness all the way down to the neck-shoulder junction.
Next to our calipers and digital scale, the Holland Micrometer is the first tool we pick up when checking out a new batch of brass. It's easy to get a quick, reliable reading and when you're finished, it stores flat in a drawer, unlike the Sinclair. Anyone considering neck-turning their cases should buy one of Holland's tubing mics (or a Sinclair) before ever turning your first case.
Both the Micrometer ($80.00) and optional mounting stand ($32.00) shown below are sold exclusively by Holland's Shooters Supply, 711 Avenue "H", Powers, OR 97466, Phone: (541) 439-5155.