AST 40mm Lowering Springs | Mercedes-Benz SL-Class W107R (ASTLS-14-1184)AST Lowering Springs for the 1972 1982 Mercedes Benz SL Class (W107R) 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