The lower suspension arm feature optimized flexing under dampening. With the shock being mounted in the middle of the arm, the load is evenly distributed onto the suspension arm, which increases the mechanical traction, and response of the car.The lower arms are made using a CFF™ - Carbon Fiber Fusion, for outstanding handling.Hard hardness of the lower suspension arms is recommended for carpet tracks and even for some high traction asphalt conditions. These will provide the most consistent handling and will make the car more free (less stopping) in corners, compared to when the M arms are used.This rear lower arm fits on left side of the car. Hard hardness.