Bowl/slide?

I bought a new bong the other day, a rather small one and I dropped the bowl that came with it. :( I was planning on getting a new one anyway, so no biggie. But I was looking on line and I noticed they're measured by millimeters, is that the diameter/circumference of the slide or what? Please help, I need to toke with this baby. :jointsmile:

diameter

and thats at the bottom part of the slide right?
like here:

it's the width of the tube.

alright, thanks for the info guys.