Molded bra cups are shaped from a single piece of material which creates a cup with no seams. This makes molded bras ideal for wear under tee shirts. The smooth, clingy nature of t-shirt fabrics and other knits requires a bra that won't show through--seamless cups go a long toward solving the problem.
There are so many styles of molded t-shirt bras to choose from that there's bound to be a good choice for all shapes and sizes. Styles include underwire, push-up, minimizers, balconets, contour (padded) and demi bras, among others. All will have smooth cups and may have other smoothing features like seamless sides, racerback construction or leotard backs.