Extruded lumber crayons last up to ten-times longer than ordinary molded wax crayons. Fadeproof, waterproof, smearproof. Won't melt in direct sunlight. Will work on wet (green) lumber or dry wood, metal, concrete and most other surfaces. Each crayon is individually UPC coded. Hex shaped 4-1/2 x 1/2 in to fit lumber crayon holders.