The underwired bra features a rigid underwire under each cup for enhanced support and a more defined shape. It's the most common structure in lingerie, suitable for average to larger busts that need steady support for everyday wear, unlike the non-wired model.
A underwired bra is identified by the semi-rigid underwire sewn into the edge of each cup, which distributes the weight of the bust and shapes its form. This is the most common construction, far ahead of non-underwired bras.
The underwire stabilises the cup and limits sagging throughout the day. In contrast, the non-underwired bra with good support relies on a wide band rather than a rigid underwire.
The cotton non-underwired bra and the plus size non-underwired bra cater to different needs: more flexibility, less structure than the version with underwire.