The U.S. National Institute of Justice (NIJ) has developed the ballistic standard considered the most commonly accepted standard worldwide. The NIJ standard spells out the various levels of protection.
NIJ Level II balances concealability, comfort and protection against blunt trauma. It can stop 9mm as well as .357 Magnums rounds.
Body armor vests meeting NIJ Level IIIA standard is the most commonly used protection in the industry due to cost, safety and because it can be comfortably worn under clothing. Law enforcement agents including police officers often wear vests with panels that meet NIJ Level IIIA standard, which protects against rounds coming in from most handguns including 9mm, .357 SIGs and .44 Magnums.
Machine guns and rifles can deliver rounds of such high velocity that soft armor simply cannot protect against. For those facing this threat level, we recommend using hard armor inserts, which upgrades a NIJ Level IIIA vest to a NIJ Level III or IV vest, offering a lot more protection.
Note that due to government regulations we are not allowed to sell and ship Level IIIA vests together with NIJ Level III or NIJ Level IV ICW hard armor panels. These products need to be ordered separately (two payments) at our website and will always be shipped separately.