A 28DD is small. VERY small. Its sister sizes are 30C and 32A. A

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Is a size 28D almost 28DD bra small for a 16-year-old? - Quora

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Adore Me Women's Cinthia Full Coverage Bra 42dd / Jet Black. : Target

Paramour Women's Ethereal Unlined Bra - Fuchsia Rose 42dd : Target

Paramour Women's Lotus Unlined Embroidered Bra - Dazzling Blue 42DD

Bali Women's One Smooth U Posture Boost Support Bra - 3450 42dd