This is an Triple slot FeatherWing connector board with the third slot tx/rx swapable for serial debugging or adding two MCU's.
Note: Slot 3 has the tx/rx pins swapped by default but can be reverted to a standard connection by cutting and soldering the jumpers. It also has the 3v3 line disconnected by default.
The triple slot featherwing is ideal for debugging and putting together a smaller project.
You will need to solder the sockets or can solder the FeatherWings directly for a more permanent solution.
There is a pre-solder option available.