J's Racing SPL damper are developed from their racing expierence from the past 15 yrs. They repeatedly over and over to obtain the damping data for their specification. All dampers are spec'ed carefully with street comfort and circuit performance in mind. 50mm piston (mono-tube) is used for high tunability ranges with 30 way damping adjustment. All dampers are made of billet CNC machined super high quality aluminum along with superlightweight springs. All kits comes with dust boots, adjust wrenches and urethance bump stop. Uppermounts are not included.