Molded foam cups and top of the line shaping with a plunging neckline, the most comfortable bra you’ll ever buy. No metal and wires that become misshapen and stab you over time - A Knix size 3 bra fits 36B, 36C, 36D, and 38B. Knix also has a hosery system that can help you find your bra size by lining up your band size and cup size on a chart. For example, if you have a 36 band and an AC cup, you would line them up to get a size 3.