Keep Good Brew From Going Bad

Using the cap is as easy as using a seltzer bottle or refillable whipped cream dispenser.  It's innovative feature is variable pressure regulation -- that can be set from zero (off) up to 15psi. On the uKeg, the cap automatically regulates pressure to continuously maintain your desired carbonation level. You don't need to manually refill or use separate filling devices. One CO2 cartridge keeps one uKeg growler full of beer fresh for up to 4 weeks.

CO2 cartridges can easily be found online at very reasonable prices.