4" BASIC SYS W/DLSS RESI SHKS 2011-19 GM 3500HD 2WD/4WD.Fabtech's new 4in crossmember systems utilize their proven heavy duty construction and design features for a robust suspension upgrade. The 4in system features high arched lower control arm crossmembers constructed of 1 4in thick steel for maximum strength. The Fabtech ductile iron steering knuckles retain the near stock track width keeping tires under the fender for a clean appearance. Rear lift is accomplished with a block and u bolt configuration.