What recommendations for food grade CO2 cartridges? I found quite a lot of choices on Amazon but don't know where to look. The application is for a mini beer growler tap. It accepts 8g and 16g. May possibly use it for whipping siphon in the future. Questions; how long do the cartridges last? What does the "g" 8g and 16g indicate? Are there any good/bad brands or are they all the same? Thanks!