Its a very heavy duty lock and chain. I think most people wouldn't bother trying to break into it, especially if locked up in a public space, like outside a shop for example.I tend to wrap this round the seat mount on the bike while travelling, and I can't even notice a difference weight wise. Sometimes it can feel a bit heavy in a backpack but nothing more than you would expect.Its a decent length too which means you can wrap it in all sorts of ways, I haven't yet come across anywhere it hasn't been able to lock my bike to. (the chains do fit through standard spokes and wholes on a bike)