Last fall we announced our new leveling and SST lift kit offerings for the all-new GM 1500 trucks. We specifically did not include the factory lift kit-equipped GMC  AT4  and Chevy Silverado Trail Boss. The  AT4/Trail Boss are factory equipped with a 2" front lift. This front lift includes a longer front shock/strut assembly. When combining a traditional leveling kit on these factory lifted trucks, several issues present themselves including binding problems with the factory control arm ball joint and contact concerns with the lower strut/CV axle assembly. The 69-3920 SST Lift Kit works with the factory 2" front lift. This kit includes a top mount strut spacer along with a pre-load spacer to limit droop and the same premium grade upper control arms now available in our 66-3921 leveling kit. OE style 3" tall cast iron rear lift blocks and rear bump stop extension cups are also included to create a true  AT4/Trail Boss-specific bolt-on lift kit that provides 2" of front lift and 1" of rear lift. This new lift kit concept is similar to our successful TRD Pro Plus 2 SST Lift Kit which is also engineered specifically to work with that factory OE suspension lift. Your trust in ReadyLIFT to provide high-quality, precision engineered products is extremely important to us. You can be assured that this all-new SST lift kits are the absolutely most reliable and best performing suspension upgrade option for the  AT4/Trail Boss trucks. AT4 - Max tire 305/55-20, 20x9 0 offset wheel Trail Boss - Max tire 295/65-20, 20x9 0 offset wheel NOTE: Use of Auto 4 HI feature not recommended.. NOTE: This GM 1500 kit is NOT COMPATIBLE with vehicles equipped with rear composite mono-leaf springs. The mono-leaf is easily identifiable the U-bolt is round/circular around the top of the leaf spring. This kit only works with vehicle equipped with traditional steel leaf springs identified by square U-bolts. NOTE: Not compatible with Sierra AT4X or Silverado ZR2 Edition.