[Arran]

If you draw a straight line between each pair of pins on an octal based tube socket, or tube, they will form a octagon, still one of my favorite tube base designs, followed by a rim lock tube, which is a European base, and the old style bayonet based tubes of the 1920s. My least favorite tube bases are of the mini seven and nine pin variety, I can never seem to get the gap in the pins lined up with the holes without looking at the top of the socket, definitely a step backward, plus all of the bent pins you have to deal with, even Loctal tubes are better.
Regards
Arran