Bra allows the wearer to use the tighter hooks as the bra stretches during its lifetime. Bras may be designed to enhance a woman's breast size, or to create cleavage, or for other aesthetic, fashion or more practical considerations. Nursing bras are designed to aid breast-feeding. Compression bras, such as sports bras, push against and minimize breast movement, whereas encapsulation bras have cups for support. Breast support may be built into some swimsuits, camisoles and dresses. Bras come in a variety of styles, including backless, balconette, convertible, shelf, full cup, demi-cup, minimizing, padded, plunge, posture, push-up, racerback, sheer, strapless, T-shirt, underwire,
Siberian Shelf Sea, and respectively subdivided into the Kara Shelf, the Laptov Shelf and the East Siberian Shelf. Eastwards it merges into the Chukchi Shelf (of the Chukchi Sea) shared by Eurasia and North America (i.e., by Russia and the United States). Westwards it merges into the Barents Shelf of the Barents Sea. Also, the New Siberian Islands and the New Siberian Rift Basin define the 'New Siberian Shelf.' According to the split of the high Arctic by the Lomonosov mid-ocean ridge into the Eurasian Basin and Amerasian Basin, the Siberian Shelf is split between the Eurasian Shelf and the Amerasian Shelf.