"B仔" are private chip dealers who provide "black" casino chips to people who are not able or willing to carry a large amount of cash to a casino. In contrast to the regular casino chips circulating in a casino, these "black" casino chips can't be cashed out directly at the casino. Instead, "B仔" will help cash them out (or change them to regular chips), or even transfer the money to a specified country, and get a cut, of course.