I was at a headshop earlier and my friend bought a similar pipe.

The owner called it a 'donut' and its primarily decorative. I'm sure it also helps to cool the smoke just a bit.
Johnny McPotSmoker Reviewed by Johnny McPotSmoker on . Newbie questions... What is that dip behind the bowl for? Nobody that I've asked knows :S I love my pipe :) I was also wondering what the deal is with all of these legal bud things are... they don't seem to say what it actually is, just that it is great blah blah blah. Rating: 5