February Challenge - Underneath

I wasn't too sure what to go for on this photo challenge. I had thought about the underneath of a car. Nah, that is usually dirty and rather dull to look at. I thought about the underneath of a bridge. All the ones round here are dull too. The tune Underneath the arches sprung in my head (I am not as old as that reference may infer!) but there aren't any arches to speak of.

Whilst mooching round the kitchen I thought about the underneath of a beer bottle. We see the bottom of bottles quite often. Maybe even stare into the bottom through the empty bottle.

It has the volume (500ml the nearest to a metric pint) and the diameter (useful for those people running bottling plants) and then some other secret codes that Google can't find for me.