When undergoing a breast reduction, there are several factors to consider. Generally speaking large breasts also have a wide base diameter. In order to reduce a large breast, the surgeon must preserve the nipple and the attached tissue that supplies it with blood flow. In addition, the skin that will be preserved must be sufficiently thick to survive. As a result, if you want to have an attractive and shapely breast, then you will unlikely achieve a B cup. However, if you want a B cup regardless of the cosmetic appearance of the breast, it can easily be achieved. Keep in mind that the reduced breast will then appear very flat. Almost like a male breast. In summary, if shape and appearance is important to you, then achieving a B cup is unlikely. But if you don't care about the cosmetic appearance of the breast, any size is possible. Think about it carefully before you decide to undergo a reduction. Good luck with your surgery.