The 8" system has more lift and super trick upper tubular control arms than the 6" system. Designed for 2001 GMC K2500/3500 heavy duty trucks. The new upper control arms feature integrated multiple shock mounting tabs should you desire the optional dual shock system, for the ultimate in dampening capabilities. Rear lift is accomplished via a 4" block and add a leaf system with rear bump stop brackets. This product ships in approximately 1 days