MightyMounts used to be available to fit specific factory cross bars. We discontinued making these around 2006. Currently the Universal MightyMount will be used to fit most accessories to factory cross bars, click here to check your vehicle.
The exceptions are;
MightyMount 32H for the Whispbar / Yakima Through, Flush, and RailBar
MightyMount 34H for Whispbar HD Bars
MightyMount 39H for use with the Yakima Core and JetStream bars
Attached is a list of prior MightyMounts and which factory bars they fit.