All ballistic and/or edged blade and/or spike resistant vests are tested to different levels and are designed to serve different uses and purposes. More specifically, a vest that is certified to protect against bullet threats may offer no protection to stab threats and vice versa.
Therefore, it is important to consider which threats you may face, so you can identify which protection levels are most suitable for your needs.
When choosing a vest, it can be assumed that a vest with a higher rating will be slightly thicker, slightly less flexible, and slightly heavier than a lower-level alternative. This is especially the case when increasing the ballistic level of the vest, as more layers of kevlar® must be present within the soft protective panels of the vest.
If level III or IV ballistic protection is needed, hard ceramic or polyethene SAPI plates will need to be added to the vest. As these plates are designed to defeat rifle threats, they add much greater weight to the Cordura with SAPI plate pocket vests (the only vest which can hold these plates).
Below are the tables issued by the NIJ (National Institute of Justice). These outline which bullets will be stopped by which levels. It also noteworthy that higher levels will stop bullets travelling at higher speeds.
NIJ protection standards might update slightly from time to time, but the changes will be minor, and will not affect 99.9% of private consumers.
It is worth mentioning that if these levels do indeed change, the vest that passed the old standard would more than likely pass any small changes.
DO NOT purchase a lower level vest than needed in the hope it will perform higher. No vest is truly bulletproof, and any vest will always be penetrated by a higher, more powerful calibre weapon.
If you need any help deciding which vest and/or size to choose, please see our 'Guide to choosing a vest'. If you are still unsure, it may be worth contacting one of our specialists directly, using the many contact options advertised.