A kind of credit card, the big card is matched with the small card, and only half of the big card has a hole hanging on the key, which is more fashionable. You can swipe your card at any time. There is not much difference. China Merchants Bank and China Everbright used to have mini cards. I like it very much. You can give the big card to mom and the small card to help yourself. There is no need to apply for a supplementary card.