Rancilio Silvia OPV rebuild kit for NON-adjustable valve
This kit is to rebuild the OLDER-Style non-adjustable valve that does not have the lock nut (as shown in this link).This version of the Over Pressure Valve is found on machines built until +/- 2006 (machines produced around 2006 could have ether style). If you do not know which version you have. please refer to the above link.
For a kit to rebuild the newer adjustable-style valve see this link.