First Sergeant. Same pay grade as Master Sergeant, but the diamond in the patch is the difference. The First Sergeant in effect runs the company, with the Captain's approval. If you like, the Captain is the Chief Executive Officer, the First Sergeant the Chief Operating Officer in corporate lingo. An SFC has two lower stripes or rockers but the three upper stripes or chevrons are the same, and no diamond. SFC's usually run the platoons and would be analgous to Directors or Department Heads.
Seehttp://en.wikipedia.org/wiki/U.S._Army_enlisted_rank_insignia
