Thin rayon material. see-through and unlined. size down as this runs large. for reference, i'm 5'4, 124lbs size 26 in jeans. in retailer clothing, i wear sz small or size 4-6. i ordered this in small, but the body and shoulders are too wide and unflattering especially with the shorter length of this top. that is why sizing is key. i know it is meant to fit loosely, but you will have to order a size down otherwise you will look larger and the dark piping details on this top will not fall in the rig