"These are the only control arms available that have spherical bearings at both ends, and yet do not require a coil-over conversion kit. MM's Engineering Team solved the problem of keeping the control arm upright, stable, and aligned with the chassis, when the springs are left in the stock location. We did this by designing a urethane "bumper" that is located around the spherical bearing, between the chassis and the end of the control arm. The bumpers are at only one end of the control arm, the chassis end. The bumpers keep the control arms aligned with the chassis, but are not so stiff as to cause an increase in suspension bind. The large Teflon-lined spherical bearings at both ends of the MM Extreme-Duty control arms completely eliminate the deflection allowed by urethane bushings during hard launches. This reduces axle windup, and allows the car to react more quickly. Unlike more commonly used bushing materials such as hard urethane, Delrin, or steel, spherical bearings allow proper articulation of the rear suspension. This eliminates torque box damage caused by suspension bind."