AFCO's Reactor Series Single Adjustable Drag Shock is an economical alternative to a fully adjustable design. Monotube design that features a wide range of rebound adjustability without bleeding over into compression changes. This 4" shock comes with coil-over hardware. 12.22 comp x 16.17 ext. length= best for 12.25"-13.25" centers at ride height. Valve range covers 1,000 hp or less applications (for higher hp check out our "Big Gun" series.) Recommended 7" or 8" spring sold separately. California Proposition 65 Statement