These were extremely popular (at least where I was from) back in the mid-'70s. I don't recall seeing them after '75. I would have worn one, but they were a girl thing and not for boys. Boys didn't wear bracelets back then. The one mistake girls would make with these things would be that they would go swimming wearing them, then the bracelets would shrink so much that they'd have to be cut loose in order to get them off. I think they still sell them, and maybe a guy could get away with wearing one these days, but I'll always think of them as a girl thing...
