They are expensive. They would help with chassis flex. I'm just putting it on here just so everyone knows that they are available because probably you would never come across these.
They have a video on the front page you can watch.
http://www.rigidcollar.com/
Fronts...
http://www.ebay.ca/itm/SPOON-RIGID-C...item4aea7cb81f
Rears...are cheaper
http://www.ebay.ca/itm/SPOON-REAR-RI...6dfcf1&vxp=mtr