All matboard stocked by Matcutter.com conforms to industry standards. They are marketed as acid free by their manufacturers. 

I really dislike the term "Acid Free" because it causes alot of confusion. "Acid Free" mats are really "acid-neutral". Technically, only matboard made of cotton fiber commonly called "Cotton Rag" is truely acid-free. All other matboard, the majority produced in the United States, is made from trees, a naturally acidic material. 

This matboard is treated with calcium carbonate so it tests "acid-neutral" with a "ph meter". Calcium Carbonate retards the aging process not only due to the matboard material but the environment as well.

All matboard will deteriorate in time with "rag" deteriorating the least. Simply beware of products touted as "100% Acid Free, Archival Mats", they are often standard core "acid-neutral mats" and are not "archival" as the term suggests. 

If you have a piece of art that is precious in a monetary or emotional sense, use true archival products you can trust or take it to a conservation expert. Conservation framing includes many factors beyond rag versus non-rag. The glues used to bind the single-ply sheets together, the type of inks used, top and bottom cover papers, presence of alum and type of picture frame and glass are all conservation issues.