Seat tube sizing?

[Fordulike]

The spec size for my seat post is 27.2mm.

Is there a standardized sizing for the seat tube relative to the seat post size?

I've been looking at front derailleurs and there appears to be a few different sizes for the clamp.

 

[Emo Rider]

Most front derailleurs will fit a variety of down tube diameters. Better front derailleurs will also come with a spacer kit to fit small diameter tubing like you would find on a road bike for instance. In my experience, unless it is specifically for a small tubed road bike, all front derailleurs will fit a 27.2mm inside diameter down tube. If it is for a carbon frame, you may have to by a specific piece of kit. I am not that familiar with those.