From my local comic store I found out there are different thicknesses of the boards, some go inside the comic and some are called backing boards which are thicker and make it sturdier, so those are the ones we'd want. i found this on a site he directed me to
http://www.comicpreservation.com/
He said he never recommends the "economy" ones for comics except for very short term use.
"Acid Free Backing Boards link
These stiff boards are made of cloth/rags or wood/paper. They are usually a little bigger than the size comic book, they are made to support. These boards are inserted in a mylar sleeve usually in back of a comic book. The board helps supports the comic, to preventing bending the book and also getting creases in it or color breaks on its cover. The acid free nature of these board helps protect the comic book from acid migration found in the aging process of paper.
Some boards come with a 3% to 4% calcium carbonate buffer at a ph of about 8.00 added to the acid free backing. The idea is to help reduce the amount of environmental pollutes from getting into the comic. Backing boards fall under the area of Archival Board in the field of document preservation and in art presentation as a support product such as mattes."
They're much cheaper at your local store than amazon, plus you can see them in person and make sure you're getting the ones you want.