Adafruit Feather M4 Express User Manual

Finally, there's the "Stacking Header" option. This one is
sort of the best-of-both-worlds. You get the ability to
plug into a solderless breadboard and plug a
featherwing on top. But its a little bulky
Soldering in Plain Headers
Prepare the header strip:
Cut the strip to length if necessary. It will be easier to
solder if you insert it into a breadboard - long pins down
© Adafruit Industries https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51 Page 18 of 183

Adafruit Feather M4 Express Specifications

General

Brand	Adafruit
Model	Feather M4 Express
Category	Microcontrollers
Language	English