Upgrade your rear end with QA1's Pro-Rear System. Available in the MOD series, double adjustable, single adjustable and ride sensitive valving non-adjustable options,each adjustment has been carefully defined to provide the ideal horse curve to maximize performance. With evenly spaced valving changes throughout the adjustment range, there are no jumps when adjusting between any two clicks. These Pro-Rear Systems are commonly used in drag racing, street performance and street rod applications. Available in Simultaneous Compresion and Rebound Single Adjustable (DS), Independent Compression & Rebound Double Adjustable (DD) or Ride Sensitive Non-Adjustable (ALN), Coil-Over, Lightweight Aluminum, Ride Height Adjustable, Spring Mounting Hardware Included, 100% Dyno Tested and Serialized, Revalveable and Rebuildable by the QA1 Factory or QA1 Authorized Service Centers, Precision Machined Aluminum Piston with PTFE Piston Band, 5/8" Centerless Ground, Hard Chrome Plated, Solid Piston Rod, Three Step Sealing System, Available to Fit 3" or 3.25" Diameter Axle Tubes, Made in the USA, , Kit includes:, (2) Proma Star Shocks or Aluma Matic Shocks, (2) Linear or Variable Rate Springs, All Mounting Hardware.