Fabtech 11-19 GM 2500HD 2WD/4WD 4in Basic Sys w/Perf ShksFabtechs new 4 crossmember systems utilize their proven heavy duty construction and design features for a robust suspension upgrade. The 4 system features high arched lower control arm crossmembers constructed of 1 4 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.