They are suppose to soften the ride somewhat while lifting the rear. They replace the OEM overload spring. I don't recall if towing capacity/payload are reduced somewhat, but seems like it would. My max towing is maybe 6000 lbs. anyway, so there is plenty of margin for my needs.
They are also supposed to reduce axle wrap, (at least compared to just using his billet rear blocks), but not as much probably as the PRG traction bars would.
Greg posted the following about them:
http://www.titantalk.com/forums/show...9&postcount=12See my sig. for a link to pics of them.
http://www.titantalk.com/forums/show...94&postcount=3
1.25" to 1.5" of rear lift, and you can reduce that by .75" if you use the heavy-duty rear shackle with them. I plan to do this.
Oh, in this post Greg was thinking of a version that would retain the OEM overload, and the higher tow capacity, while improving the ride:
http://www.titantalk.com/forums/show...03&postcount=8
http://www.titantalk.com/forums/show...85&postcount=5