This shows the different 6ba terminals around the meccano system in the electrical set's time. A)- is the terminal nut for the 1920-24 side lever motor-it has a different shape than the #306 terminal and is domed on top. B)- is the #306 electrical set terminal nut. Compared to A, there IS no comparison. Don't confuse them! C)- is the elektron set terminal nut. Different animal altogether! Are we straight!!!!