Pre-cut mats made from clay coated paperboard, white one side 22" x 17" outside/12" x 18" art size - 12 mats per package. Paperboard surface is neutral ph. Smooth, non-glare finish. Mats can be decorated with oil and water-based artist paints, mediums, inks, watercolors, markers, pencisl crayon etc. Board thickness is 18 ply. Mats have straight cut, non-beveled edges.