I'm still working on practice skin but as I've been reading about sterilization practices I see the terms "membrane" or "Backflow preventer" a lot, but while browsing cartridges I don't see any place advertising those features on their cartridges. Is that not a thing anymore or is it assumed that all cartridges now have membrane/backflow preventers? I will have access to an autoclave once I start but I feel like this is still valuable info? The less mess in my machine the better, right? Anyways does anyone have recommendations for trustworthy cartridges with reliable membranes?