Bruce, as a point of interest, you wouldn't go from a 34A to a 38C, you would go from a 34A to a 34C. The letter is the size of the breast, so if it gets bigger, the letter goes higher up the alphabet. The number, while not actually the circumference of the rib cage immediately under the breasts, is representative of the part of the bra that has to go around the ribs to stabilize the cups.

SRS