Yes those are the grommets. I just push the cart & grommets all the way through the tube (pushing on the connector end) to remove them (being careful not to damage the center post on the connector). Oh and take the fill screw out first. Just takes a little force.
I just started using these tanks with my Provari about 3 weeks ago and now I have 5 of them filled with Mop & Pop juice and loving them.
Thanx so much for the help. I've now changed the cartos twice and it really was a snap. Can't believe how intimating it all seemed but I was soooo afraid of breaking it. I'm such a pro now (chuckle, chuckle) I think I'm going to HAVE TO order a few of the minis - this one is always stuck in my face. Just love it - thanx again.