Yep, thats what I heard. The "s14" version with the one arm does fit on the s13, but I heard it doesnt have the stability the s13 needs and gets from the circle ones.
The ride is pretty stiff on full soft, but streetable. Sliding, is another story, this thing is so easy to slide now. During mid drift it feels more controllable. It has minor(MINOR) body roll, and I still have 9 more adjustments to make them harder.
I set the preload on the springs just a little, so there isn't too much. The car driving day to day isnt too bouncy, but going over some stuff it just rattles your teeth. The car scrapes all speed bumps, even if I go over them sideways (i just have to jack it up a little but im too lazy).
Overall, this is the best money I have spent in a good while. Cheap, awesome build quality, great customer service, it performs, and they are pretty. Im going to start buying PBM stuff from now on.