This is what I found from CCGK website using Google translate:
http://www.chinaccgk.cn/product/11.html
Name : Bulletproof alumina ceramic plate
Material:A120+PE
Color: black; other colors can be customized
weight:NIJIII (2.4KG), NIJIV (2.7KG)
size:250*300mm
Protection level:NIJIII, NIJIV
Warranty period: 8 years
Insurance: Ping An Insurance 3 million
product manual:
Alumina ceramics have the highest density, but the hardness is relatively low, the processing threshold is lower, and the price is relatively cheap.
According to the purity, it can be divided into 85/90/95/99 alumina ceramics. The higher the label, the higher the purity, the higher the hardness and the price.