I didn't have a 18mm deep socket for use on the plugs, so I used the plug socket in the tool kit. I got all the plugs out without problem, but I did re-shape the other end of the plug socket. 3/8 socket too small, 1/2 socket too large, so I turned it using an adjustable wrench.
My question: will an 18mm deep socket (round in shape), fit into the opening on those two cylinders with hex-shaped opening, which works dandy with the tool kit socket?

(sorry, couldn't resist)
My bad. I was impressed I had typo'edso few words,
and got carried away.