MCU Card is a standardized add-on board, which allows very simple installation and replacement of the microcontroller unit (MCU) on a development board equipped with the MCU Card socket. By introducing the new MCU Card standard, we have ensured the absolute compatibility between the development board and any of the supported MCUs, regardless of their pin number and compatibility. MCU Cards are equipped with two 168-pin mezzanine connectors, allowing them to support even MCUs with extremely high pin count. Their clever design allows very simple usage, following the well-established plug & play concept of the Click boardâ„¢ line of product.