These trays are made with our patented .065 MicroChamber/Silversafe material. We have chosen this board because while the majority of the tray is composed of our pH 8.5, buffered MicroChamber paper, the inside is neutral in pH, non- buffered, white, lignin- and sulfur- free cotton paper, with a very strong, abrasion- resistant surface. Since we do not know what specimen may finally be stored in these trays, we feel most comfortable offering a non- buffered interior environment. Certain collections, including protein- based artifacts, are safest when stored in a neutral environment; and buffered paper can cause metal artifacts to corrode due to the salts formed when alkaline buffers neutralize acids. They fit neatly in standard specimen cabinet drawers measuring 29.625 x 23.25 x 1.875in.