An underwire bra is a brassiere that utilizes a thin, semi-circular strip of rigid material fitted inside the brassiere fabric. The wire may be made of metal, plastic, or resin. It is sewn into the bra fabric and under each cup, from the center gore to under the wearer's armpit. The wire helps to lift, separate, shape, and support a woman's breasts. Many different brassiere designs incorporate an underwire, including shelf bras, demi bras, nursing bras, and bras built into other articles of clothing, such as tank tops, dresses and swimsuits.