Drop forged baseplate versus the traditional cast molded one, hollow axel, hollow kingpin, I think that the back of the hanger has been bevelled out to Mark II status, and Indy is trying to change the image of their bushings (finally) and went with some that more closely resemble Venture bushings, which do make a difference. I went from traditional Indy 149 to the new hollows and think they are well worth the money, definitely an adjustment period because of the weight difference.