Buffered with calcium carbonate, this high-alpha cellulose mat board offers a bright white core. It meets all standards set out by the FATG and PPFA in its respective category. PPFA Class III. Made in Canada.Additional information:What is a mat?A mat is a piece of cardboard (usually with an opening in the centre) that leaves a space between the photo and the frame. It is only suitable for paper artwork, not canvases. When a mat is used, there is usually a glass panel to protect the photo and the mat. Finally, when you see the words "acid-free or conservation", it means that the mat is archival quality and will not fade, yellow or alter the work over time.