Bra Type

T-Shirt Bras

A T-shirt bra uses a rigid, pre-formed (moulded) cup designed to give a smooth, seamless line under fitted tops. The trade-off is that the cup doesn't flex to match your shape the way a soft or lightly-lined cup does.

Construction

The cup is moulded as one piece, usually with no visible seams, and holds its shape whether or not it's being worn. This is what gives the smooth look, and also what makes fit less forgiving.

Common fit challenge

Because the mould is rigid, it can gape in places a soft cup would simply flex around. This is a construction property of the style, not automatically a sign the size is wrong.

What to check

Before sizing down, check whether a soft-cup style in the same size gapes in the same place. If not, the moulded construction itself is the more likely explanation.
Compare cup height and shape (not just size) between moulded styles if one gapes and another doesn't.