Smartly designed, the inner arm seams and front panel seams are forward of midline so no rubbing. Material is light, breathable, sweat wicking, drapes well.
Love it enough that I bought a other color, I decided it was time after putting this on again and again while still wet from the wash (not that it takes it all that long to dry or that you have to wash all that often, the merino definitely helps keep you feeling less funky even for doubles days ;). It's an excellent layering piece for under a vest with mittens for very cold high output conditions. Not very wind resistant so I pack a shell in case for longer runs. Enjoying climbing and lifting in this too. Grateful that the arms are long enough that the thumb holes aren't just decorative, I'm 160lb, 5'11" long limbed / muscular for reference and am in a size large, don't like my clothing skin tight.