According to Bilstien, the only difference between the 4600 and 5100 is that the 5100 is for 0 to 2 inch lift and the 4600 is for stock height. Also the 5100 has a brushed aluminum look and a rubber boot, while the 4600 is painted yellow and has no boot. Either one should give the same ride. I just put 5100's on my F250 with no lift, mainly because I think my air bags might overextend the shocks when running empty with a lot of air in them and I like the idea of the boot. Oh, and the brushed finish just looks cool
