I have no idea it doesn't say just that its non toxic. I'm guessing it is some type of metal like bismuth or something similar that would be used in nontoxic shells. Its primary use is training for LE or shooting 3 gun competition so you don't get bounce back on steel targets. No sure what I will do with it not a three gunner but I will find something appropriate for it to be used for. Guess I will have to shoot some wet phone books and see what happens.