... openings. Professional quality. Economic Price. 1. Mat board (matboard, pre-cut mat board, mount board, bulk Mats,card board) ... 2. White core, black core,c ream core mat board3. Lignin free and acid free4. Thickness: 0.5mm ... 6. Multi layers and multi openings7. 4*6", 5*7", 8*10", 11*14", 27*31" and other sizes ... colours9. Professional quality and economic price. photo frame mat board / double mats