[[File:SBC Lynx-J53-J54.png|thumb|center|300px|J53-J54]]
[[File:SBCLYNX_ADDON_XUAL Mounted.JPG|thumb|center|300px|Example of mezzanine usability]]
J53 and J54 are 10x1-pin 2.54mm-pitch vertical headers for optional mezzanine expansion boards. These boards can be implemented to extend SBC Lynx functionalities and/or interfaces.