As part of the experimental USB support, a new device stack has been added to the Zephyr RTOS since version 3.3.0. Existing implementations of the USB classes (or functions) will be ported to the new USB device support (porting should be completed by presentation time). The USB device stack itself does not provide any useful functionality. The functionality can be provided by a class implementation like CDC ACM. There are USB-IF class specifications, like CDC ACM, or third-party specifications, like the Bluetooth HCI transport layer. New USB device support has a common API to interface with class implementations. A vendor-specific class or function must also use this API. The API will be mandatory for all new implementations. The stack also has management functions, such as adding or removing a class instance to or from a configuration at runtime. Johann will give an introduction to the new USB device class API in USB support, show how to implement a simple function that supports multiple instances, and briefly describe the API. The author will also cover relevant differences and features in the new USB device support.