the Secol A-S system is THE best. Costs about USD 1 a sheet. The top one on the page is the bees knees. http://www.conservus.ch/webexplorer.cfm?id...=1?id=63&tlid=1 It is a Brit company and is usually used by museums, private buyers seldom buy them. Polyester is the only way to go, but there are different kinds of polyester, different qualities. I did not buy the special binders, that would be going overboard, but I have some really big office binders. The sheets above will take an A4 doc with space to spare. There are even bigger ones.