Stillman & Birn Archival Quality Sketchbooks - Delta Series Wire Bound - This line of archival quality sketchbooks has a simple premise: When it comes to sketchbooks, paper matters! All of the books in this line are beautifully bound in the United States. The covers are extremely solid and the books literally feel different in your hands than sketchbooks made by other companies- these have a weight and sturdiness that you will notice right away. Made entirely out of archival materials, you will love these books. The Delta Series wire bound sketchbooks are suitable for wet media and mixed media renderings. The paper is 180lb. (270gsm) ivory and has a rough surface. There are 25 sheets of paper per sketchbook.