I have the ones with the grommet. They work great in the milk jug, just drill a hole and push it in and it's watertight (I still can't believe how easy that was). From what I understand the screw-kind are better in thicker plastic like buckets?
chicas_red&pepper :
I love that idea! But my problem seems to only get worse! your cages must be huge! I have a rabbit cage that was altered to make it a 'chicken coop.' It is kind of lame... There is a roosting bar and the feeder I have hooks on the wall, they are only locked up in this...