Last year, I purchased a set (front and rear) of Level IV plates from bulletproofme.com.
They fit just fine in my Interceptor, but when other plate carriers were used, the rear, which was countoured differently than the front, would not fit.
Even after I had owned them for 6 months, the company offered to swap out the rear for a front plate (for a 20% fee – very reasonable in my opinion, since they would have had to X-ray the plate before reselling it).
However, I decided to test the plate myself, and see if it really did what they claimed – stop multiple shots of .30-06 armor piercing ammunition without any supporting soft armor.
The plate did indeed stop 3 shots of .30-06 AP (163gr hardened steel penetrator projectiles courtesy of Rich_V on AR15.com), as well as many other rounds.
The plate allowed part of one .308 projectile, as well as 4 5.45x39mm projectiles, to penetrate.
However, these hits were in rather close proximity to other impacts. Because this was a ceramic plate, the initial impacts fractured the plate (it’s designed to absorb the impact this way) and the later projectiles “slipped through” the cracks.
Even after it had been shot over a dozen times, and it had literally come apart, it still stopped XM193 5.56×45 and a 12ga slug.
Overall, I’m very impressed with the performance of this plate, especially considering the cost ($270). I’d still probably wear soft armor underneath the plates, given the chance, but at least I know that the plate exceeds the manufacturer’s claims.