These extra durable Drop-Front Boxes are designed for the long-term protection of prints, documents, artwork, and similar valuables! All Drop-Front boxes are made of TrueCore board (tan .060, with a pH of 8.5 - 10.0 or black .049, with a pH of 8.0 to 9.5). Both boards are buffered with calcium carbonate, 3% reserve. The tan board is light-fast and non-bleeding. The black board is pigment-based and light-fast. Both boards are acid-free and lignin-free, high alpha-cellulose purified pulp. Both pass the P.A.T. These heavyweight boxes have metal reinforced edges for added protection. Each box has a fully removable cover and a drop-front bottom so the contents can be inserted and removed safely, without bending or damage.