The functionality and fit of the two Q-Tower models are the same on all vehicles prior to 2007. Until that time, we fit vehicles with both towers: new (P/N 8000124) and old (P/N 8000105). Starting with a handful of new body styles for 2007 and moving forward, we fit vehicles with the newer version of the Q-Towers only. If the vehicle requires the new towers, you will see fit note #180. If you have model number 8000105 and are fitting a vehicle that has fit note #180, then you will need to upgrade to model 8000124. Q-Clips work the same way with both models.
The main difference between the two is in design. The new Q-Tower was improved by: 1) connecting the shroud to the body as one piece instead of three and 2) tightening the tower to the crossbar with a wedge instead of a cam thereby strengthening this point and easing installation. Please take a look at the attached PDF to determine which model Q-Tower you have.