Comic Pro Line's (CPL) boards are precision cut to size and are produced from Solid Bleached Sulfate (SBS) which is a bleached virgin wood pulp. SBS is the highest quality and most expensive paper board substrate that is also Acid-Free. ComicProLine Backer Boards are quickly becoming a favorite of comic collectors worldwide! Once you experience the quality and thickness of these boards, you will never use anything else! They are truly that good!