Dixon Lumber Crayons last up to 10 times longer than ordinary molded 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 individually UPC coded and hex shaped (4-1/2 x 1/2 inches) to fit lumber crayon holders.