Mod 1

Hello,

Sorry if this is a dumb question but I didn't know where to ask...

What is "Mod 1"?

I know it's a size of gearing. I assume it's like 32 pitch or 48 pitch but rather than being a certain pitch it's "Mod 1"

If anyone knows what it means or where it fits in the pitch scale I'd be curious.

Also - why does one use "Mod 1" is it for more strenght? Where? And what products typically are of this size.

Thanks!

DM