There seems to be a limited number of manufacturing facilities worldwide for nitrous oxide, at least for cartridges available publicly.
There are at least a couple of sources in Europe, and one in Taiwan, for the manufacture of nitrous oxide gas. I don't have any experience with the Chinese source, I must confess I have a slight prejudice against Chinese products, having seen some Chinese manufactured health supplements testing out with substantial impurities. Might be a different case with the gas, though. Info would be appreciated. Some of the Chinese brands include BestWhip, Mr. Creamy, and EasyWhippets.
The brands that I would recommend are the ones where the gas is manufactured in Belgium and then put into cartridges in Vienna, and there are some basic EU standards for purity. To be honest, I think the purity is for the gas manufacture itself, as opposed to the gas you can get out of a cartridge. As near as I can figure, there is no difference between the various brands produced by those factories. Rather, the differences seem to be cosmetic changes for brand marketing.
My favorite here would be Ultra-PureWhip.
ISI is said to be good, but they charge more (I believe there is more brand awareness), and yet come from the exact same factories. SFG and Sexxy Whip come from this source as well, but the cartridges are shiny chrome and I find them slightly harder to keep track of in use. I also find larger boxes (50 count) more difficult to deal with than the usual 24 per box. EZ Whip I haven't tried.
The brands that I don't recommend come from Hungarian/German gas manufacture with cartridge manufacture in Hungary. Typically, this would be the regular PureWhip brand, for example, as well as some cheaper generic unlabelled product. Apparently there is some kind of oil that is I guess part of the cartridge manufacture, and once in a while you get some really oily cartridges from this source. Pretty nasty.
The distributor I deal with should be pretty easy to guess from a bit of web searching. I didn't really want to link to them considering the off-label use I recommend. Once you've ordered with them they should offer you some price discounts.
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