Your package is sent before a panel of senior SNCO's and officers. They then review it and based off of what officers who were your boss in the past marked your and said about you. Its the best system we have though it is very flawed. In my job there is no promotions for Master Sergeant and if there ever was I am no where near the top to be considered, even though I have been in my current rank for 6 years. I put First Sergeant because I wanted it plus the above reason, some select First Sergeant just seeing what will happen, and sometimes they get it, and that is bad. I did not get selected ad it was because I have a 260 PFT, the board wanted a 275 or higher. How fast you run shouldn't be the end all but it is evidently. I have led platoons into combat and in friendly environments. Then I met guys who got First Sergeant who have never had a platoon or did a special duty assignment, so how the board saw that person as more suitable is beyond me.