Timbrenwas founded in 1965 on the premise that suspensions could and should work better. In that year it acquired the Canadian patent for rubber torsion suspensions. In 1968 Timbren introduced Aeon rubber springs and began manufacturing SES Suspension EnhancementFeaturesImproves Ride and HandlingEliminates Trailer Sway and RollEasy Bolt-On and Pop-In InstallationMaintenance FreeSatisfaction GuaranteeLifetime Provide Variable Spring RateSelf-DampingSimple Design ApplicationsVibration IsolationSuperior Ride Quality To Other Types Of Suspension 98-04 F250 & F350 Superduty 2WD & 4WD Rear Suspension Enhancement System- SKU: MYRD72717 This product ships in approximately 1 days