Percolator bongs are hose-less water pipes with built in smoke twirlers for greater cooling. They come in various forms with (Tree, Dome, Shower-head, UFO, Drum and Honeycomb percolators)
Diffusor bongs have attachable smoke diffusors, down-pipes or adaptors with multiple slits, holes or in the form of a shower-head. Through the additional swirling the path the smoke takes is lengthened and thus, the smoke is cooled as well as filtered. More descriptive information as well as photographs are available under: Bong Academy 2