You're thinking of Andronov-style fins, I own a Leaderfins Hyper Professional which is built in that style. The fin I was talking about was this one, mainly because they're cheap and durable. Very good to experiment with. The russian fins like Kershov, HyperFin and Andronov are good, but bloody expensive and take forever to get to you. Another option is the very good Chinese-made Chen Bin fins. They'd also be safer in a game, but really, that's a very relative statement.