The couters / elbow cops and the outside splints are made from 0.040"/19ga./1.0mm 4130 steel. The inside splints are made from 0.032"/21ga/0.8mm 4130 steel. The plates were heat treated to a Rc48 hardness by heating them to 930C/1706F and quenching them in water. The plates are then tempered at 260C/500F for 1 hour. From what I've seen the plates should resist denting as well as unhardened mild steel at least 3 times their thickness.