Aluminum MIC-6 is cast plate known for its stability and consistency between plates. It has superior flatness and dimensional tolerances on the thickness which makes it popular for tooling and base plates. Aluminum MIC-6 is a registered trademark of Alcoa. This is s slug from a big plate we needed to cut out. It has holes for a 5/16 cap screw at .326 thru and a cbore of .500 at 11.250 Blot circle . PLATE IS 11.970 ROUND