Lavia 18 Retro Style Abstract Print Dress

This LaVia 18 Retro Style Abstract Print Dress is in beautiful preowned condition colors on the dress include gray, black, blue, and brown sleeveless side zipper 100% cotton outer nylon lining no stretch measured laying flat: pit to pit 18" waist 15" length 39.5" I can't find a size but since this fits me I will say it's a small or size 6 please compare the measurements I have taken to a dress you already own