This is the most comfortable helmet i have ever had (and i've had quite a few). Super secure and light weight enough to not notice. I have used it in the desert, cool mountain mornings, hot high elevation afternoons and as of yesterday a spring mountain snow storm. Fantastic helmet and very flattering. I have already recommended it to all my friends. As far as sizing goes i have very thick, long hair (dreads) so i sized up to the M/L from my regular S/M i have for my giro helmet. The size chart for POC is right on point. The fit is very flattering and i love the amount of protection for the back of your head especially for more enduro style riding on big mountains. I dont think i will ever buy another style helmet, no more sit-on-top helmet fit, this has got to be the best out there.