All the o-rings should be installed in your cap when you get them. The ones that came are extra replacement o-rings. The two smaller ones are for the inside hole in the cap where the carto slides though. The 2 bigger ones are for the outer part of the caps. They send spares because you can tear the inner ones pretty easy if your not installing the carto nice and straight and with some kind of filler tip. Im not sure where your putting the other ones (the spares) but they all should be installed in your caps already. Just wait until you get some ikenvape cartos that are not flanged then you will really be screaming as if you push them in to far slightly when installing them they pop out of the bottom and get juice everywhere. Also I would put a couple drops on the carto on the top and bottom where they slide into the caps before insalling, a little liquid for sliding helps. Dry cartos don't like going threw the o-rings very well, believe me! So lube em up helps tons!