The Downstem

The downstem can be omitted in a homemade bong, but it allows for further customization, like a diffuser, or a USB port. whatever.

Maybe roll a blunt while you're at it...

Plastic-
Example- cigar tubes, highlighters, etc.

Pros-

• poke a billion teeny little holes with a soldering iron for a nifty diffuser!
• its enough of a bitch to use any other material that I haven't found it even worth it, you should email me some if I'm overlooking anything.
  
• take a bic pen and wrap tape around it and you can make an awesome pull mechanism for your bowl/stem like so:

Cons-

• douche bags bitch about plastic all the time
• slightly more effort, so dont worry about it for a temporary bong.