Pinit BACKINGS for British Quad Posters. 30 x 40". .028" thick Acid-free Board. White both sides. Long-term Storage. SKU: KAF28BQP (0)No Reviews yet Add to Shopping Cart Details This material is acid-free all the way through. Acid-free board can trap migrating acids in paper and neutralize it. Details Back DetailsThis material is acid-free all the way through. Acid-free board can trap migrating acids in paper and neutralize it. Reviews 0 Back Ratings & ReviewsNo reviews availableBe the first to Write a Review