not sure, its some form of metal, its very strong and its not that heavy either. We got it with the car, i tested it at mondello last day (
Well i made a mistake and put it to the test) hitting an grass bank with an stony underside (first corenr same place where everyone inlcuding Carnegie Launched his Car in 2002) i thought it might have damaged the sump from the big bang but it only marked it and it didnt move.
Its 16.38mm thick according to the thingamy bob measureing thing i have here.
We are changing to an lightweight high strent Mix sumpgard which is 8.2mm soon