03 and up 4runners and 05+ Tacoma's and FJ cruisers come stock with a 29 spline pinion. They also changed the driveshaft flange form the older style to a larger size to accommodate a larger spicer u-joint. The aftermarket gears for the rear of these vehicles are 27 Spline. This flange allows you to install aftermarket gears and bolt your driveshaft up. This flange is required on all 03 4runner and 05 and up Tacoma's and FJ Cruisers that are to be regeared. The cheaper triple drilled flange has the correct spline count but does not have enough width or the correct bolt pattern to allow it to be used.