You need a Hong Kong dollar card to directly deduct Hong Kong dollars, and all the others are converted from RMB into US dollars and then into Hong Kong dollars. I used to spend money in Hong Kong by swiping BOC International's Hong Kong dollar card, which means directly deducting Hong Kong dollars, and swiping Minsheng visa's US dollar card prompts you to pre-authorize the local currency. It will be several days before the bill shows the deduction of Hong Kong dollars, resulting in currency exchange fees.