I've been a collector for 36 years, and a dealer for 26 years (and an ebay seller for 7), and the most common question I get is "Are your bags and/or boards acid-free? Well, pretty much all plastic bags for comics, magazines, etc...are today made from polypropylene, which is plastic-based (in the 1970's, we had to use the cloudy polyethylene bags, which were oil-based, and would harm your paper item over time). I've been carrying "Fun-Yet" bags since 1980, and they are the best bags I've seen, with strong seams, excellent clarity and a full 2.4 mil thick. I still have X-Men's that were bagged with "Fun-Yet" bags 20+ years ago that show no effects of damage from the bags. To my knowledge, polypropylene bags are not acid-free (even though I see dealers claim that in ads), but I think they are still safe. I recommend mylar covers for your more expensive comics, as they are totally acid-free. I have seen all the backing boards that are offered on ebay, and none of them are acid-free, even though some dealers claim they are. The fact is, you can't buy an acid-free board for a nickel. You can buy acid-free backing boards, but they will cost you .50+ per board, depending on thickness. I recommend those again for your expensive comics. In closing, have fun with your collection, and don't get too uptight about your item falling apart...it's most likely tougher than you think. To check out "Fun-Yet" bags, visit The Comic Zone ebay store.