For future reference,

NEMA ML-3R 3-pin midget twist-lock female

1-11/64" diameter

NOTE - The ground pin is FEMALE

example - Hubbell 7484

NEMA ML-1R 2-pin midget twist-lock female - 31/32" dia

NOTE - no ground pin

example - Hubbell  7464V

Having opened my big mouth, I am now sure I have mistyped something - double check to be sure..........

Cheers,