This tank top is a three panel tank and not meant to wear by itself. On the chest and bottom the material is made of cotton, so that tank top won’t compress the chest, and the bottom section won’t roll or ride up. The mid section is made of polyester and spandex which tightens and gives compression to the mid section.
You can wear it over your bra, top or any other clothing. It goes a little smaller in size but that is for the purpose of compression I guess.
As for the nursing moms it is very convenient as it has a cross over top for easy excess.
It does give your body a nice shape.