As the only layer in summer conditions in the Sierra temps from 40-80 during the day. I was looking at all the weights and the Tech Lite shirt is down to Superfine 140, some places it is 150. Trying to get something that will hold up to the abrasion of wearing a pack and will dry out when washed in the afternoon. It would be rotated with another shirt. I was at the end of my lunch, so couldn't post much info on the original post. I have a set of heavier Ice Breaker stuff which worked out great in Yosemite over NY's.