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

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

Bra Sister Sizes + Sister Size Chart

Why can't I find my bra size? I've tried 32a, 32b, 34a, 30c, 34c

Bra Sister Sizes + Sister Size Chart

What is the difference between 32C and 34B bra sizes? - Quora

What is my bra size?

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Cosabella Never Say Never Curvy Sweetie Bralette

True & Co. True Everybody Women's Adjustable Strap Scoop Neck Bra - Sage M : Target