How should an aero road helmet fit compared to a standard road helmet?

Fit is even more critical with aero helmets because the aerodynamic benefits depend on the helmet sitting in the designed position. The helmet should sit level on your head with the front edge just above your eyebrows, and the tail should tuck close to your neck when in the drops or aero position. There should be no gap between the helmet's rear edge and your neck. If the helmet sits too high or the tail sticks out, you're losing aero benefit and may actually be slower than with a standard road helmet.