In the last few years, many sports outfitters have come up with all kinds of artificial fibers that are supposed to transport the moisture away from you body and make you feel dryer. When you are going for a hike, down the slopes or rafting, these are totally fine but they are really ill-suited as an undershirt for a dress shirt because they often come in patterns, bright colors and always with a contrasting logo that will be visible through your shirt.