240D Starter (Allen) bolts

[RalphinSL]

I need to replace the starter on my 82 240D. I'm out of town and away from most of my tools; I know I'll need an allen socket to remove the main two allen bolts. I can't tell what the socket size is; I hope it's 10mm but it feels more like 13mm. Can anyone tell me? (For those who helped me earlier, I was able to replace and bleed the clutch master cylinder. Thanks)
Ralph