AST Suspension Lowering Springs - BMW G20 M340 RWD and XDriveAST Suspension Lowering Springs For BMW G20 M340 RWD and XDrive Part # ASTLS 21 031 AST Lowering Springs are manufactured from a premium high tensile chromium silicone wire which is handpicked by AST engineers for its quality and metal consistency. Each spring is cold wound and then heat treated to increase hardness and reduce internal stresses present after winding. Each spring is then individually shot peened, phosphate treated and then powder