Yes, of course, the Fritz Box provides the Internet connection. One of these mesh routers is then connected directly with the WAN connection of this router to a LAN connection of the Fritz Box. After that, the mesh system from Xiaomi will provide the WLAN. The WLAN of the Fritzbox must then be switched off and the accessibility in the entire house or flat for WLAN devices should then be available everywhere. By the way, each Xiaomi mesh router has an additional 3 port Gbit switch built in and up to 10 such Xiaomi mesh routers can be used as an extension. The system is very powerful and can manage up to 256 devices.