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.