The Expedition Notebooks Are Made With Yupo Synthetic Paper - A Material That Is Waterproof, Tear-proof, And Resistant To Extreme Temperatures. Making This Notebook Virtually Indestructible And Perfect For Any Adventure. Dont Go On Your Next Expedition Without Your Field Notes. Please Note - Because The Pages Are Waterproof, Writing Is Best Done With A Pencil Or A Standard Ballpoint Pen Such As A Fisher Space Pen.