2007-2021 HD Rear Air Suspension Kit (HP10128)Description Have you ever noticed a difference in ride control when driving empty vs. driving fully loaded? That is because your truck's factory suspension was designed as a compromise between capability and comfort. So when you are hauling heavy loads, the rear springs can be pushed to the limit. The result can cause an excessive bounce, sagging ride height, and an overall feeling of instability. You can easily solve this problem the simple addition