I have a set of Timbrens on my 2011 F350. They came with a life time guarantee and I have had them on my truck for 6 years. You have to set them up so the overloads are just touching when the camper is on. This gives you three points of contact on either side. It was a major improvement and reduced the sideways rolling on the highway and off-road I don’t have to stop the truck after every big dip to let the sway stop. The Timbrens came with a shim but I did not need it. If the overloads are not touching, there is no point in using them.