You really have to try them on. One of the guys at my LBS said just go with the Echelon so I tried it on...well it didn't fit. the ProperoII wasn't out yet but they had a bunch of last years S-Works so I tried those as I have an older Specialized Decibel which fit great and was the predecessor to the S-Works helmet line. Well it didn't fit right either. The medium was too small and the large was too big in both of those helmets. So finally I tried the Prevail and it fit great. So that said I would have gone with one of the lower helmets had they fit right...but they didn't. The Prevail IS lighter for sure and supposedly has better airflow. So you just HVAE to try them on...go for fit first then decided among the ones that fit whether you are going to spend more money or not.
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