MGB tappets adjustment

["Alberto Manganini" <albertom@tin.it>]

I've bought the ClickAdjust, but need to buy the 1/2" drive socket. Now, I
don't want to remove the cover just to see which size of socket I should
buy, neither want to buy a full set of 1/2" drive socket just to get the
right one (I already have a full 3/8" set). Hence my question is: which
size of socket is required to adjust the tappets of a 18GB engine?
Thanks for your precious info

Alberto