The MicroPython WBUS-EMMC module has 4GB of eMMC flash storage and fits right underneath all pyboard D variants. This way it can be powered and controlled by the 40+40-pin WBUS header.
The two 40-pin mezzanine bus connectors are added on the back of the WBUS-EMMC to make it fit right between an adapter board and a pyboard D. All IO pins on the WBUS are passed through from the top connectors to the bottom. Use WBUS-EMMC as a replacement for an SD card, for high reliability storage.
Learn more about how to use the EMMC 5.1 (HS400) 153B 4GB here
This WBUS-EMMC replaces an SD-Card. It's not possible to use an SD card and the WBUS-EMMC together.