If you are looking for a "piece" to prevent or address a nipple slip (an accidental exposure of the nipple), there are several functional items—often called "wardrobe essentials"—designed specifically for this purpose.
What to Wear Under Swimwear to Prevent Nip Slips | Butt-Chique Guide nipple slip
: Products like chest binders or certain sports bras often include a built-in breathable sponge layer specifically to prevent nipple slips and ensure a flat, modest appearance. If you are looking for a "piece" to