The castel 9000 graphite black lead pencils are made of very finely ground graphite and clay making them perfect for all your professional sketching drawing and design needs they are coated with eco friendly water based varnished and have a special bonding agent for break resistant leads thanks to the clay and smooth graphite consistency the castel 9000 pencils are never scratchy and will give you the control you need when working on the small details as well as larger areas of your drawingt