Jun 20, 2014 #2 DUQ Flashlight Enthusiast Joined Jun 22, 2005 Messages 1,824 Location Ottawa, Ontario, Canada I'm pretty sure it would/is just over 18 mm. I have one so I'll measure for you.
Jun 22, 2014 #3 leon2245 Flashlight Enthusiast Joined Apr 4, 2008 Messages 2,335 Great, let me know if you get a chance to confirm. Can't find unbored a19's anymore.