They are a closed-end long chrome hex, with a round end with a very shallow cone. 7/16-20, 3/4" wrench size (they look similar to the very long ones used for the bolt-thru wheel covers). There are also 13/16" versions around, that have a more rounded end. They have more meat on the seat and look fine. Both are RH and LH thread. Not sure if you can get the 3/4" ones new any more — mine are all pretty beat.
I think the LH studs are still listed in the Dorman catalog which you can find online. Different for drums and discs, as someone noted. I have at least 5 LH rear axle drum studs that I pulled, and probably some K-H disc studs as well.
