It goes like this. You reach 50, you pick a spec. 10 ranks relating to that spec become unlocked. As you rise through them, you will unlock armour and a weapon skin related to that spec.
Finally, at rank 10, you will unlock the Tactical Package or Support Package related to that spec, which you may equip anytime, and you can choose another spec, which will not take away any of your unlocks. Questions?
When do you unlock other specs? --- Gamefaqs: The most passive aggressive place on the internet.