seat clamp bolt size?

[foz]

Am I right in thinking that the correct bolt size for the seatpost clamp on frames with 'fast-back' or 'shot-in' type seatstays is M6 with 1mm pitch?

I mean the type where the bolt goes through the top of one seatstay and threads into the other stay. I have the old, rusted one, and from my measurements I measure it as M6 x 20mm with 1mm pitch, but I'd like to confirm this before I go ahead and buy a new one!

Thanks!

 

[Old Ned]

They may vary, I'm sure I have different ones depending on age and make of lugs etc.