Underwire bras include a thin, flexible u-shaped wire inserted into the fabric of the cup to give added support to the bra. All bras designed to give a particular shaping to the breast (pushup bras, demi bras, strapless bras, etc.) include an underwire. For women who wear larger cup sizes (DD and larger), an underwire bra featuring a cup with an encircling support panel (or sling) is recommended.