2" PVC coupler

Fits tightly, but not water-tight (unless you add a filament-friendly sealant.

Can be used as an extension to table legs from this project:

http://www.thingiverse.com/thing:1111686

If you found this useful, please share your work and be sure to peruse my other submissions which are almost as varied as they are many:

http://www.thingiverse.com/3E8/designs

Enjoy!