Designed for the purpose of providing strength and support to the breasts, these come with an underwire at the bottom of the cup. They were initially made with a thin wire but are now also made of plastic and metal. They are meant to round off the shape of your breasts and contour any unwanted bulges. You might see a lot of articles floating around to question if an underwire is advisable to begin. But there’s no conclusive result so far. However, the only thing that matters is the quality your brand provides.