AST Suspension Lowering Springs (30mm/30mm TUV) - 2004-2011 Mercedes-Benz SLK-Class SLK 200 (W171)AST Lowering Springs for the 2004 2011 Mercedes Benz SLK Class (W171) 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 coated to outlast even the life of the