I've been using cartos for a while now in tanks and they have been great, I'll be moving on to rebuildables later but that is another story. I'm curious if anyone has dissected pictures of cartos, boge preffered. I tried googling it and only found pics of filler material unwraped. Im curious about the coil in the tube. Is it a straight line or coiled? I'd like to have a better understanding of how they work. Thanks guys.