This item was previously and exclusively available for the F104X1 chassis. It is now available as a standard option part for all versions of the F104 chassis. This unit incorporates a side damper which eliminates the standard friction discs found on the standard F104 F1 chassis. The roll damper offers better consistency compared to the traditional damper discs as the applied damper grease is shielded from track debris and stays within the damper tube. Item 53901 TRF Special Damper (F103GT) (separately available) is required for use with this set. If installing this Option Part on an F104 PRO chassis, the kit-standard damper can be used. Friction damper and friction plates cannot be used with this set.