Molded bras feature cups that disappear and are invisible under close fitting t-shirts and form fitting tops. Molded bra cups are shaped by a heat-machine process that duplicates the natural breast shape. Molded bras can feature a single layer of fabric or be heat fused with a thin layer of foam or fiberfill to provide a stiffer, non-collapsing cup shape. Since molded bra cups are permanently shaped, they may not be the right bra for everyone. The cups tend to be rigid and may not encase the breasts properly, especially if a woman has wider breasts. If this is the case, you may want to consider a seamless bra instead of molded to achieve the same "smooth under knits" benefits.