When making books, or boxes or any other cartonnage project, a bone folder is always a great helper in the process, especially made in Teflon material. They are very resistant and don't make our projects "shiny" as traditional bone folders made out of bones do.
Great quality, high durability material, folds without burnishing or damaging the projects.
This is for 1 Teflon bone folder size: 5 1/2" x 5/8" (13.5 cm x 1.5 cm)