I purchased this for an upcoming long distance hike as one of my layering options for really cold days. I ordered my normal WoolX size and it fit as expected with room to layer a light-weight long sleeve and a mid-weight long sleeve underneath and not look or feel bulky. Very thin for what it is, not much thicker then a mid-weight top. Removed 1 star = NO thumbholes in a heavyweight base layer top? Mid-weight/Heavy-weight tops are used in temperatures thumbholes are needed. PLEASE ADD THEM BACK