1,non-toxic;no dust. 2,natural mineral without any chemical ingredients. 3,1pc slate pen equals 20pcs common chalk for using. ... OB-50white2400191739*39*28Features1,slate pen,the same function as traditional chalk.2,which is made of natural mineral without any chemical ... of mini blackboard,chalk board, whiteboard, writing & drawing boards,color clay,slate pen and so on. Our company takes quality as the ...