Made by gypsum powder material, safe chalkboard chalks are for use and great for most surfaces, such as white board, chalkboard and more. The ergonomically designed chalk body is convenient for you to grasp and use, suitable for home, school, office and more.FeaturesColor:Assorted ColorMaterial:Gypsum powderSize:10.50X2.50X2.20cm4.13X0.98X0.86in The chalk is safe for use by children and adults, and is easier to clean up after use, very practical and convenient. Abundant quantity of chalks, enough to meet your daily and replacement use, can also share with others. Our Outdoor Use Chalk can get your children outside to play and give them the opportunity to bring a variety of artwork outside. The chalk is made of reliable gypsum powder, which can write or paint on the chalk board smoothly. The chalk set has a wide applicable occasion, making it perfect for art projects, school, and other applications.Package list: 40 Chalks