Choosing the Right storage bag for a collectible vs a non collectible can be confusing and can cost you more than you need to pay. Most bags are plastic-polyetheylene(PE) or polypropylene(PP), with these categories futher broken down by high density products,mylar, and others. If you are storing low value items then common polyethylene (PE) bags will work. They are economical, good storage for a few years, and are soft and pliable. (PP) products are generally better suited for food or paper products, are acid free,, and generally are thinner with a much higher clairity. Mylar-also acid free, is best for long term archival storage but is stiffer and expensive. If you are storing low value collectibles, (PE) is Good and economical. But if you are storing rare and important items-use (PP) or mylar-mylar being the best product generally available.Please remember, hoever that Ultimately; no bag or product will product your items, if left in direct sunlight, moist or wet conditions....