Stretched on kiln dried stretcher...
Crescent No. 300 Illustration Board is a medium weight, professional grade board with high rag content and a medium surface. Each board is 16-ply and 0.055" (1.4 mm) thick.
Crescent No. 99 University Grade is a cold press illustration board that is economically priced and has a medium textured surface. Each board is 14-ply and 0.050" (1.3 mm) thick.