93-00 HONDA TRX3004X4: Progressive 512 Series Rear Shock The 512 Series was the first aftermarket shock made specifically for Utility ATVs. They have undergone extensive R&D to provide the finest possible suspension for your workhorse vehicle. We use improved spring rates for heavier load stability and handling over rough terrain as well as increased length for more travel and ground clearance. The 512 Series comes with an adjustable spring preload to accommodate different loads (i.e. mounting a plow or carrying a hay bale).