So you are looking to lower your 2014 to 2018 Chevy Silverado or GMC Sierra 1500 but you're not sure what kit or control arms you have? Here is how to determine that so you can order the correct lowering spindles or struts.
GM decided in 2014 to come out with a new Aluminum control arm for their trucks on some models in addition to the standard cast steel control arms. Below is the differences in those 2 control arms. You will also notice the third option which is brand new for the 2016.5-2017-2018 and up trucks. These are known as the AVV code stamped HD control arms.
The easiest way to tell if you have the new AVV stamped HD control arms on your 2016-2017 Chevy Silverado or GMC Sierra is to look at the back of the lower control arm. The AVV HD Stamped arms will have a big weld connecting the 2 pieces of the stampings as seen here-
As a general rule 2014 to 2016 GM Silverado/Sierra 1500 models could use any of the 3 styles of control arms and 2016 to 2018 models use aluminum control arms.