"load equalizer" between the 2 springs on the trailer axles. This little chunk of metal is to help equalize the load on each axle however when you see a trailer going down the road unlevel the axle on the low end of the trailer will have more weight on it. Scale each axle on the trailer individually and you can see the difference. This also means those 2 tires will have more weight and run hotter going down the road. Rule of thumb if the side walls of the tires on the unit are hotter than what you can holds your hand on for 10 seconds they will likely have a catastrophic failure. Hope this helps.