ReadyLift offers model specific wheel spacers designed for 07-UP Chevy Silverado and GMC Sierra 1500 6-lug trucks and SUVs with the ReadyLIFT 4" SST Lift Kit. These 1/2" quality spacers are precision CNC-machined from 6061-T6 billet aluminum for maximum strength and longevity and are HUB Centric.. Wheel spacers are required when using the factory GM wheels and the 4 in. kit to properly space the factory wheel away from the suspension. Each wheel spacer is both hub centric and wheel centric to insure the absolute perfect fit with your hub and wheel. You will not find a stronger wheel spacer in this size anywhere on the market. When installed the wheel spacer will place the outer wheel lip in line with the fender. The wheels will not stick out using this spacer.WARNING CA Proposition 65: YesWARNING CA Proposition 65 Message: WARNING Cancer; Birth Defects; and Reproductive Harm www.P65Warnings.ca.gov