BELL Stratus MIPS Adult Road Bike Helmet - Lightweight & Ventilated Cycling Helmet for Men & Women - Perfect for Commuting, Road Biking & Cycling Adventures

The short answer is that this helmet is comfortable, well-ventilated, and was highly rated by a study from Virginia Tech. Buy it.I bought this helmet because my existing one was a few years old and a Virginia Tech study was recently released that scientifically evaluated several different bicycle helmets, and this one made it into the top tier of helmets providing the best protection.I'm not certain that I believe you need to replace your helmet after 3-5 years as is recommended by the manufacturers, but it won't hurt anything but your wallet. Similarly, some believe that the MIPS system is unnecessary or even counter-productive. The Virginia Tech study suggests otherwise and most opinions seem to be that it is potentially beneficial. Of course no lab measurements can fully test for all the possible crash dynamics.My wife's measurement of my noggin and Bell's fitment guide indicated that I needed a large, which surprised me since I am not a big guy. Nor do I have a disproportionately large head. So I ordered a large and I must say that it does fit great. It easily adjusts with the wheel on the back of the head strap and the chin strap adjusts easily too. It is a noticeably better and more comfortable fit than my previous Bell which was just whatever seemed good at Target.Ventilation seems more than adequate, indeed at times with the sun at my back, I can see the vents in my shadow on the pavement.I ordered the purple one because when I ordered it that color was somehow $38 cheaper than all other colors. Go figure.If not this one, at least wear some helmet and come home safely from every ride!