They have been around for some time. Ive seen them on tractors and trailers. Not to mention cement mixers and the like. What they do is save weight in the driveline, then add more to the load. Which means the total weight of the rig over all is the same. Just watch,, you will see them. There are real bouncey. Looks like the driver is fighting them all the way. Good move maybe if they didnt increase the load. LMAO I think they will prove unsafe for the trucker and for the public at large. The hunks left from one of those tires blowing out is unreal. It could total a Civic and disable a 1/2 pickup.