I love mock turtlenecks also. I have a mesh one that I got at BPS about 5 years ago, haven't seen them again since. That is my go-to shirt for when it is hot. I have a whole drawer of other mocks that I wear though. If nothing else, they keep my bino harness off my neck, allow a place to tuck in a facemask, and keep bugs out. For when it is not just plain hot, I wear a mock T and then a button up.