Wow! Yes, these T-shirts do help keep me cool, and help 'keep my cool', as I tend to get distracted when I sweat profusely. They are most effective when I am moving. This is my first experience with cooling shirts that actually deliver. The fit is quite good too: I read on Amazon about the size running smaller. Not true. And they stretch too. They do not change after a wash either. No color fade, no size change. Very light weight, with a silky smooth feel like polyester, but do not cling to you when you sweat.
Yes, they wont be much use if the ambient humidity is high, or/and there is no air flow. Also, I wish AC made T-shirts from the material 'Elegear' makes amazingly cooling blankets-- continuously cool, no matter what. I eagerly wait for that day ...