In Spec Ops: The Line's multiplayer, as players level up they get different types of faction-specific armor for their classes.
Tier 1: ACV and PALS VestEdit
Both vests offer zero protection from incoming damage, as well as give no movement penalty.
Tier 2: OTVEdit
At Tier 2, both teams share the OTV vest. This is the first set of armor that actually protects from damage, blocking 15% of incoming damage. However, it comes at the cost of suffering a 4% reduction to speed.
Tier 3: OTV w/ SAPIEdit
Both teams share the same Tier 3 armor as well, the OTV w/ SAPI. As with Tier 2, it offers an increased damage reduction of 30%. However, it also gives an 8% reduction to movement speed.
Tier 4: MTV w/ E-SAPI and IOTV w/ E-SAPIEdit
As the final tier, both sets of armor grant the highest protection, with a 45% reduction to incoming damage. However, it also give the highest movement penalty, with a speed reduction of 10%.
The Ghillie Suit is unique to the Sniper class. While it offers no damage protection, and thus no speed reduction, it also allows the sniper to blend into their environment, becoming almost completely invisible if he doesn't move.