Equalizing Air Pressure w/Hydrophobic Filter

[50ShadesGreyMarket]

Posted as a response to someone on another thread but since I spent the time to set up this demonstration I created a new topic. Feel free to ask clarifying questions or add your own suggestions if you do it differently. These are 23g needles and I got both to fit in a cartridge stopper without coring.

ignore sanitation, this is for pics only

Remember: you can only push or pull air with hydrophobic if it stays dry.