Our X23B is a 2012 and the clearance between the vent pipe and the vent was a bit tight. The cover (Maxxair II) fit but I had to install it slightly off center due to the limited clearance. Works great! We only close the vent when it's really cold outside, so that means it's open 99.99% of the time - in storage too.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks