Click to Zoom To support the large 4 pin 211 and 845 family of valves we have numerous valve bases. SK4X50-S: shielded large 4 pin valve baseLarge 4-PIN chassis mount, nickel plated connections, highly glazed white ceramic, with protective shield for rim lock types. Used with 211, 845 etc… SK4X50-S-G: shielded large 4 pin valve base, gold contactsLarge 4-PIN chassis mount, highly glazed white ceramic, gold plated connectors, with protective shield for rim lock types. Used with 211, 845 etc…