[NWFLConservative]

Correct me if I’m wrong, because I and a USA Grunt do not keep up with USAF ranks but

E7 - Master Sergeant
E8 - Senior Master Sergeant
E9 - Chief Master Sergeant and Command Chief Master Sergeant

[SoldierDad]

Each of these ranks also have a “position” of First Sergeant that is designated with a diamond between the upper and lower chevrons.

[Mr.Unique]

Correct...and of the top three can also be a First Sgt.

[KC Burke]

Air Force
E-9 is a Chief Mater Sgt., First Sgt, or a Command Chief Master Sgt. all with three upper chevrons.
E-8 is a Senior Master Sgt. or a First Sgt. but each has only 2 chevrons at the top.
E-7 is a Master Sgt or a First Sgt. but has a single upper chevron.

See:
http://www.defense.gov/about/insignias/enlisted.aspx