AST G90 / G99 M5 Adjustable Lowering Spring KitAST G90 G99 M5 Adjustable Lowering Spring Kit Part # ASTALS 21 017 conventional lowering springs. You no longer have to be satisfied with a fixed lowering height. AST HAS systems allow you to adjust the vehicle ride height with the integrated height adjuster even after the kit has been installed. All driver assistance systems and comfort features of a factory adaptive or electronic suspension remain operational and work harmoniously with our vehicle