Mr. Gasket Solid Steel Motor Mounts are recommended only for competition applications. This .180 inch thick, zinc dichromate plated solid mounts do not have the flexing present in rubber or even polyurethane engine mounts. This prevents lateral engine movement or twisting in high horsepower and torque applications. Nor will steel mounts break as easily as stock rubber mounts can. Engine movement in applications like this can cause contact of engine components into places they do not need to be (like headers hitting the frame of the car). Also engine twisting can cause severe drivetrain misalignment affecting shifting or even power transmission to the ground. However, without the insulative effect of rubber, vibration can be substantial and thus solid mounts are not recommended for the street.