This will be for heavy not for medium. Same cover as freight train put stronger core numbers.
If this ball with an F77 coverstock is for heavy oil, what is the Incinerate with an F90 coverstock (& the same core) for?
Joe,
I suspect with a longer pin-PAP drilling and possibly a P1 weight hole (and/or polish, if needed) you can make it usable for less than true heavy oil. There are lots of adjustment options, if needs be.