I wore these on a 4 hour bike ride on a 70 degree F sunny day in Colorado. They provided great sun protection while staying nice and cool despite breaking a sweat. I can't wait to wear these hiking. Great alternative to applying (and re-applying) sunscreen all day. I am a tall woman with long arms so I was a little worried the S/M wouldn't be long enough. I shouldn't have - they were plenty long even when I pulled them almost all the way up to my armpits. The M/L would have been too big for me. This size stayed up all day and I never had to adjust them.
Fort Collins, Colorado