Im not sure what you meen by the (stock, 4", 6") but the 2.5 inch shackle flip versus the 4 inch flip do have construction differences. the 4" flip puts the pivot hole in the stock position but allows for the flip. the 2.5 inch pivot hole is higher than stock hence the shorter lift. you can get a 4 inch lift with the 2.5" flip kit if you use an extended shackle. I guess that was your question.