All very good replies. I'm wondering what the real-world difference is between aero helmets. I saw the Bell Z20 and got interested because I use a Bell now and it fits wonderfully. I have never thought about it while riding. Great ventilation. 5-star VT rating. But will the Evade III at $300 offer that much more in aero quality over the $120 Bell Z20, to justify the price diff? These are the questions that keep me staring out the window late at night.