NIJ Level IV refers to the highest grade of personal hard plate armor. This armor is designed to withstand high-caliber AP round like the .30 M2AP.
Very. It will absorb at least a single shot from some of the most powerful anti-personnel rifles, including the Soviet B32 7,62×54 API and even 30-06 Armor Piercing rounds.
Depending on the size of the plate, NIJ Level IV can weigh less 5lbs for the smallest (and most expensive) Boron Carbide plates, SiC in mid-range, and over 10lbs for the largest Al₂O₃ plates.