What is the most common bra style?

The most common bra style is a t-shirt bra. These are traditional cup and band bras that feature a sturdy foam demi cup and come in both underwire and wireless styles.

They get their name because they're designed to be worn under t-shirts, which is another way of saying they're the perfect everyday bra. When you think of a bra, this is probably the style that comes to mind.