Vehicles.
You know how guns have damage and accuracy and all those stats.
Well, you see, you balance the stats the vehicles have.
So instead of Tier A vehicles.
It is tier M, Whereas M = Military.
So on.
The stats are like, Damage Capacity, Speed, Handling, Acceleration, Does it do damage, etc.
There doesn't just have to be 1 thing in a pack.
Hence the name "Pack".