The tip of the birch forest in Hongdian is thinner, and that in Heidian is thicker than the birch forest, so the tip thickness is different.

Pen is a widely used writing tool, which was invented at the beginning of19th century. The nib is metal, smooth and elastic, and it writes quite smoothly. On the mouth of the pen cap or the surface of the pen tip, there are obvious trademark numbers and models. According to the way of water absorption (inking), it can be divided into dip pen, fountain pen and ink bag pen.