AST BMW F40 M135i xDrive Lowering SpringsGive your BMW F40 M135i xDrive the extra stance it needs with AST lowering springs. Available in two configurations, depending on how much you want to lower your vehicle's ride height by. If you want a more practical setup for daily driving, choose the higher option. If stance is your primary focus, the lower setup is for you. AST Lowering Springs are manufactured from a premium high tensile chromium silicone wire which is handpicked by AST engineers