If I remember, I'll run the calipers on my Z32 when I get home. Actually . . . I have one in my bag on a black C2 (kind of an "M2 Lite"). . .
On my desk ruler, it comes in at a shade under 35mm... call it 34.5mm.
On the SAE side, it's just about 1 3/8 inches, 1.375". This is the smooth part before the grooves, which do stand off a few thousandths of an inch.
That's eyeballing a ruler, so I'll wait to get home and use the calipers.
Edited to add: The calipers I have dial right into 1.36".
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Edited to Add:
So I got my F26 and F11 from Lighthound. Works great. Interestingly enough, the Surefire OEM wrapper for the F11 states that it fits the 8X, and M2. Well, it doesn't fit on an M2 bezel, being that the Z32 and M2 have different diameters. Al's list was actually more accurate than the SF wrapper!