Very good question, and yes, Gorilla web site sucks for technical information. Only thing I can find is a length difference on the cheaper one, which may be a problem? I know the BDX work because I have them on both the Hellcat and Durango. Other difference I found was BDX says "bulge" conical seat, while the other says "standard" conical seat. Comparing the photos (if they are accurate) shows the spline location to be different too? Confusing.