disco 1 300tdi block core plug?

hi all, only a quick thread to ask,does anyone know the size of the 300tdi core plug that run along the side of the block? no one seemes to have the size and i dont want to take one out to wait for days to get the right one,so i wanted to find the rite one,i have a 50miller but i dont want to knock that one out and find that its too small!

does anyone know,if so help would be much appriciated!

thanks,tom