If you are a frequent rider, I recommend against the one-size-fits-all helmets. Getting a great fit is difficult and a good fit significantly improves your saftey. If price is important to you, look at the cheapest models that come in at least 3 sizes. Also, learn to customize the fit for your head, including pulling the straps tight in both the front and the back. If a small tug on the front or back can pull the helmet off your head, then it may be useless in a crash.