Dixon Lumber Crayons last up to 10 times longer than ordinary moulded wax crayons. Fade-proof, water-proof, smear-proof, these crayons won’t melt in direct sunlight. They will work on wet (green) lumber or dry wood, metal, concrete and most other surfaces. Each crayon is hexagon shaped, and 114mm x 13mm. PMA Certified non-toxic.