I believe there are only two common size, right?

You could just go in there and ask to see the 2 sizes, stick your finger in them to get a good feel for the size (heh) and you should have a very good idea which one yours compares to.

Another thing that usually is a giveaway is the size of the bong to begin with. If it’s somewhat small, then it will obviously have the smaller of the 2 slide fittings, but if it is in between 2-3′, it could be very well up in the air on what size it is. Anything larger than that will be the larger one.

I’d hate to have you drive across town with a bong. No matter whats been smoked out of it, I would imagine blue lights are not going to like it. Hard to swallow a bong, haha!

use a tape measure and measure yuor  slide  hole just take the measurment with and a tape measure to compare the slides

They usually won’t let you, no matter how clean.  Like everyone said, there’s 2 sizes, 14 and 18.  14 is pretty much the standard whereas 18 is normally considered the oversized joint.  There’s a pretty big difference between the 2, if you compare them you will most likely be able to tell which would fit. 

good luck  Stoned Quotes let us know what happens

use a tape measure and measure yuor  slide  hole just take the measurment with and a tape measure to compare the slides

If you look around you can prolly find something like a oversized pen to get an idea of the diameter. Then you can bring the pen
in with you & have a referance. A drill bit set makes a great size guage.

Get a blank sheet of white paper.

– trace the circumference of the piece

– take traced out sheet to headshop.

– Have them match the piece to the sheet of paper.

– Go home or somewhere safe and test it out.

-Report back.

I think my piece is an odd ball. I’ll likely purchase another one. Thanks guys!

Even if the new slide is too small it will work fine

Sounds like a good reason for a whole new bong :biggrin