Here's the pic for that tool

and the dimensional sketch

A = 3/8" Drive Size (and I think that's for clarification, surely it's 3/8" internal/female, not as pictured. Then B is not called out in the dimensions, so I can't tell if it's the outside diameter of the socket "shell" or the hex size of the plug, which they show as 13/16". The C = 5-7/8" and I take it the knurled surface lets us start and remove the plug by gripping it with our fingers.
Am I right about all this? Is the outside diameter ("B"?) meant to fit so closely that the plug is forced to be in alignment with its threaded hole?
I have yet to see a V10 plug. I would have thought they'd be 5/8" hex, but the Snap-On link indicates 13/16". Hmmm
I'm at 5" with my 13/16" (Penncraft! Anybody got one of those?) plug socket and a 3" 3/8 extension. At $70 for the Snap-On socket, I'll epoxy my two together and if I can't separate them later, Oh-Well.