I've used this binder for as long as I can remember, and its by FAR the best binder I've ever used. Its so comfortable and at the same time binds REALLY well. Its completely flat for me!
They also last really long! I still use the binder I bought 2-3 years ago. Obviously, its a little bit stretched out, but it still works like a charm! And since its stretched out, I can wear it at the gym/when I want to chill, because its not so tight.