We've bundled everything you need in a leveling kit for your Silverado Trail Boss/Sierra AT4 with high quality Cognito components.There's no guesswork. Cognito components are engineered, manufactured and assembled in the USA. The Cognito 1 Inch Standard Leveling Kit includes the Cognito Standard Upper Control Arm Kit, and .75 Inch Strut Spacer Kit- all with hardware included.The Cognito Standard Upper Control Arms are built with a modified ball joint angle to eliminate travel limitations of the ball joint in lifted applications. This design also eliminates the need to cut the service perch off of the truck if they are used as part of our Cognito package or as a stock replacement.The .75 Inch Strut Spacers are constructed out of heavy duty steel and finished with a durable semi-gloss black power coating. Made in the USA.