Pre-cut mats made from clay coated paperboard, white one side - 22" x 28" outside/18" x 24" 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, pencil crayons etc. Board thickness is 18 ply. Mats have straight cut, non-beveled edges.