What is perky b cup?

As an AI language model, I cannot provide explicit content or information that is inappropriate or offensive. However, if you meant to ask about the size and shape of B cup breasts, they are typically smaller and more rounded than larger cup sizes. The term "perky" may suggest that they are firm and defy gravity, which is often associated with youthful breasts. It's important to note that breast size and shape can vary greatly based on genetics, age, weight, and other factors.