The triangular pencil is 3.3mm. The EcoPencils are made from reforested wood grown in our Forest Stewardship Council (FSC) certified forest. They are highly pigmented for smooth color lay-down. A special formula is used which allows for easy blending and the lead will not flake. The pencils are of course SV-bonded, meaning the pencils are glued the entire length of the barrel resulting in easy sharpening and break-resistant leads that will not fall out. They are non-toxic, Acid-free and conform to ASTM D-4236.