Stillman & Birn Zeta softcover sketchbooks are flexible, yet strong with sewn bindings and rounded edges.White, extra-heavy weight 180lb (270gsm) paper has a smooth surface that is suitable for pen & ink and dry media.The paper also has internal and surface sizing, allowing it to accept light washes, wet media, and watercolor as well. Paper is pH neutral, lignin- and chloride-free.Dark purple cover with 26 sheets.