I love lightweight long sleeve shirts as a base layer for lots of different outdoor activities, but also just for hanging around. I have tested LOTS of base layers (including both those made with synthetic and natural fibers), and I think this is now one of my favorite synthetic base layers. You can wear this as a standalone top for sun protection on a hot day, but it is equally nice as a base layer when adding other layers on top. I have also come to like this shirt to work out in. This does everything that you'd want in a technical base layer (i.e. wicks moisture away from the body), but I've found that it is more comfortable than many others. Most synthetic base layers/sun shirts I've worn feel terribly clammy once you do start to sweat; this one doesn't. This shirt performs better than others I've paid double for; well worth your purchase.