I have the shackle flip n switch from DIY4X , but have yet to install it because I need leaf springs. I bought mine with the 4.5 " shackles, but since I am running 56" springs, my shackle angle might not be ideal, so I might just have to order the 6" shackles to get it right, but til I put it all together I don't know.That is what the option for 4.5 or 6 " shackles is for though, I think , to use either for different spring lengths to get the rear shackle angle where it needs to be.