Dirt Logic 4.0 Resi Coilover. The Dirt Logic 4.0 provides the ultimate in hardcore offroad dampening capacity with superior highway comfort in a big package. This massive high end shock is designed for full size vehicles that required the biggest and best Coilover shock in a bolt on configuration. Nothing else comes close. Features: 4.0in OD Stainless Steel Body. 3 5/8in OD Billet Aluminum Piston. 1 1/4in NitroSteel Black Piston Rod. Cold Wound Coil Springs. Adjustable Coilover Construction. 3/4in Spherical Ball Mounting Ends. 4.0in OD Aluminum Remote Resi. Extended Length - E25.31. Collasped Length - C16.81. Stroke Length - S8.50. Top Mount - B2 . Bottom Mount - B1.