I am sz 8-10 & purchased two of these in sz Large to wear with leggings. The weight is great for wearing under a jean jacket when it is 50s to 60s, over a thinner merino tank in the 70s, and alone withe sleeves pushed up when the afternoons inch towards 80. The brand holds up well if you exercise a little care in the laundry. In other words hand wash or wash on delicate with other soft knits rather than piling it in with jeans, etc..  My only complaint is that I ordered grey and received charcoal. Love my navy the best.