Growlers are awesome. Instead of recycling beer cans or bottles you take your growler to your favorite brew pub to get it refilled over and over again. Not saying that recycling bottles or cans is bad, just that bypassing the whole recycling thing all together is even better. Besides, fresh beer on tap is always better than canned or bottled.

I am fortunate to live near several craft breweries so I always keep a couple empty growlers in the car in case I have the opportunity to stop by and get them filled with an interesting and/or delicious brew.

The problem is that, over time, bouncing around in the car the ceramic will tend to chip the glass so they won't seal anymore. At that point you have to buy a whole new growler which defeats the point and costs money. If you close the cap it won't chip but, it'll shorten the life of the seal and if there's any moisture trapped inside critters will likely grow and spoil your delicious beverage.

This is a vented protective cap to extend the life if your growlers. Not necessary, but it would probably be appropriate to print this in beer filament if you have it.