For all "XK" six cylinder through 1987 and all V-12. Manufactured by XKs Unlimited. Sold Per Each. Chrome-Moly valve spring retainers are stronger and lighter, these chrome-moly performance valve spring retainers have other advantages as well. Their precise manufacturing eliminates the tendency for the retainer to ride up over the keepers, lifting the valve shim off the valve, allowing the possibility for all sorts of calamity. These are a must for high RPM race applications, and advised for any street overhaul as well. These retainers are suitable for all "XK" six-cylinder engines from 1948-1987 and all V-12. They allow fitment of valve stem seals to pre-1969 engines as well.