I saw that one from ebay too. I think they work great although the loose wrapping does suggest low-cost manufacturing. +1 on the free 10x13 trauma panels for each pair of ceramic plates bought. But hey, looks won't stop bullets. Overall for the price, they look like a good deal.
I also saw Sturmgewehr's videos or armor plate testing. Check them out on youtube. Be sure to also watch the part 2.
On part 2, he'll test the ceramic and dyneema plates on a dummy. Notice the cracked mannequin chest even without penetration. That's serious blunt force right there.
By the way, I have read somewhere before (can't find the link) that Germany's SK standards (equivalent to NIJ Ballistic levels) have a MUCH lower Back Face Deformation (BFD, the temporary inward collapse a panel will suffer after taking a hit) quota (US NIJ 44mm BFD to Germany's SK 20mm). This means that equivalent German plates might pass less BFD-based trauma on the wearer compared to NIJ-certified plates. I am not 100% sure about this but if you really want a plate that addresses this, it's worth a look.