Different CO2 cartridges?

I usually buy Umarex branded CO2 cartridges at my local store, 25 cartridges for 15 €.
I've seen online there are cheaper ones if you buy like 50 or 100 ones, but they're different, seem less shiny, and there's only "Umarex" written, not all the small safety phrases and such... Sometimes they're labeled "Umarex by Airstream" , and there are other labeled only "Airstream" even cheaper.
Are them all the same so I can just buy the cheaper ones, or there are "hidden differences?"