The only time I used a bong with a carb was when I bought a bong that looked really cool, but in reality it was a total piece of crap. It was a plastic double chambered bong, I thought it looked cool with all the tubes n stuff, plus it had a neat green color....but the thing really sucked...

I'm guessing any decent bong maker will make it as a slider, and the only bongs with carbs are the cheap crappy ones, (cheap as in quality that is).

I just got a new bong a couple weeks ago, nice little glass bong with a slider of course, and I love it Easily clear the bong with every hit...just cant do that with a tiny little carb hole