Upholstery Marking Chalk - C.S. Osborne No. 88 Clay-based chalk from the leading manufacturer in upholstery tools, C.S. Osborne. makes it easier to erase! Other chalks that are not clay based will leave a grease mark on cottons and other fabrics. The Osborne No. 88 Chalk also works on glass vinyl that other chalks do not. Due to the shape of this chalk, a sharp marking edge is maintined. Contains 12 chalks: 8 White chalks, 1 Red chalk, 2 Yellow chalks, and 1 Blue chalk.