A tray includes a first slot and a second slot. The first slot is for placing a first digital card including contacts. The second slot is for placing a second digital card including contacts. The second slot is defined in the bottom of the first slot and is smaller than the first slot. An opening is defined on the bottom of the second slot. When the first digital card or the second digital card is placed into the tray, the contacts of the first digital card or the second digital card are exposed through the opening. When the tray is received in a connector of an electronic device, the exposed contacts of the first digital card or the second digital card are electrically connected to the connector of the electronic device.