Board Thread:Theories/@comment-25322628-20151225034754/@comment-26091912-20151226130422

EternalLocket wrote:

There's also the general belief by fans, I'm not sure if it was mentioned in the manga, that Betolt's Titan is like the Wall Titans. So if Bertolt's Titan is taller than 50 meters, then maybe the Wall Titans are also taller than 50 meters.

Hopefully they manage to talk more about Wall Titans in the future, because they really haven't said much about them. They most likely will next few chapters, seeing as Reiner was hiding in the walls, which means Titans in the walls will become relevant again at some point.