You need to have such pills with you in case you cannot find drinkable water or water of questionable quality and origin!

Very small pills for 1 liter per pill. You take them out of the blister like traditional pills almost. I got them for cutting water, so I have to throw 7-8 at a time, so time-consuming and difficult, but you can't find bigger ones for now... It's ideal for small quantities, of course.