this isnt a bong but its a pretty good pipe...get an elbow joint pvc pipe, and get another peice to fit inside it and cut it about 2 inces long. glue it in with super glue and put some aluminum foil on the end of the elbow and push down till its about like a bowl for the screen. get a needle and poke holes in the foil and use electrical tape to keep the foil in place. do a lil finishing touches and voila u got a pipe. Hits really good but the only prob is the foil flaking of in youyr lungs.

and for gravity bongs put somwe rubbing alchohol in it...it hits hard as hell