Pro Art Watercolor Paper Blocks are filled with professional grade watercolor paper that has a strong, rough surface that is sized to withstand repeated washes and scrubbings. The specially-treated neutral pH sheet enhances the brilliance of your watercolors with the best possible archival characteristics. This Watercolor Block is glued on all four sides and supported with a strong backing. You can paint on each sheet without having to stretch it or to worry about the paper buckling. Cold Press. Acid Free. 9 x 12 inch. 140 lb. 15 sheets.