This interactive marketing simulation emulates the product design process at Capital One Financial Corporation. The firm has a variety of different products (12 versions of a credit card) and detailed information (summarized by a single credit score) on several thousand potential customers. The question at hand is which product(s) should be offered through direct mail to which customers. Student teams plan and implement two rounds of mailings of up to 12 different product solicitations to as many as 750,000 prospects. They enter their round-one decisions into an online form, receive round-one results from the same web page after an appropriate delay (simulating actual mailing lag time), and last, enter their round-two decisions. The profit achieved by each team is revealed during class. The simulation illustrates the "test cell" marketing process and the benefits of product tailoring. A teaching note is available to registered faculty. Note: This simulation is based on "Capital One Financial Corporation: Product Design" (UVA-M-0506).