It gets one star because it contains six metal cubes and another star because it's basically the same size. The dice are probably made of brass, lead, iron, copper, aluminum and zinc. I say "probably" because I can't verify what's what, so it's not very useful. Also, one of the cubes is covered in stains. I have them for talks, but they're just as useful for that as they are for tutorials - not much. So now I have six metal cubes on my desk that I can't even start a conversation with other than "Yeah, I have no idea what that is." Even a damn sticker on each would have earned this a 4 star rating. Rating made, but no. According to the other people answering the questions, I just need to do a little math and weigh a little and go through some density charts to figure out what they are - ok right?