Gallon Jug Cap

This is a simple cap for a gallon jug. I was thinking of using something like this for brewing or some other DIY project. I made one with a hole big enough to fit a 1/4'' or 6 mm tube through.

I tested the one without a hole by filling a gallon up and holding it upside down for a minute. I didn't see any sign of leaking, so it is at least somewhat water/air tight.