PERFORMANCE TWIN TUBE SHOCK. Fabtech Performance Shocks have been designed to work in conjunction with each of our suspension systems, resulting in superior ride control. Features include high velocity 9-stage valving for excellent dampening capabilities and a closed cell insert to reduce shock fade at high speeds. Features: Twin Tube Hydraulic Construction. 9/16in Hardened Chrome Piston Rod. 1 3/8in OD Piston. Closed Cell Foam insert. High Flow 9 Stage Valving. Extended Length - E20.39. Collasped Length - C12.11. Stroke Length - S8.28. Top Mount - S1 . Bottom Mount - S1.