NIJ Levels - US National Institute of Justice NIJ Ballistic Levels Protection ( NIJ Level IIA, NIJ Level II, NIJ Level IIIA, NIJ Level III and NIJ Level IV). NIJ Levels or threat level, protection level is the biggest factor while choosing body armor for safety and security. Security Pro USA is your #1 Trusted Source for Officer Supplies, Bulletproof Helmets, Bulletproof Vests, Body Armor ...