Just had a new chain installed. I just noticed that the rivet (pin?) heads on the master link are like all the others in the chain on the outer side, but the master link pins on the inner (facing the wheel) side are round, not flattened. Is this the way the master link pins should look, or should they be flattened on both sides? You can tell where I'm at with this question - I don't want the master link flying off! Thanks!