This knob does come with the spring. It will fit the older version Silvia's, but there have been some reports that, depending on the position of the valve inside against the frame, as it is slightly wider, the knob shaft rubs up against the front panel. Some adjustment of the valve against the frame may be required.
Spring also sold separately.
WARNING: This product can expose you to chemicals including lead, which are known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.