A case of large-sized pens contains 180 pieces.

A case of medium-sized pens contains 240 pieces.

A case of small pens contains 360 pieces.

In 1564, in a place called Barrowdale in England, people discovered a black mineral called graphite. Since graphite can leave a trace on paper like lead, the trace is much darker than that of lead, people called graphite "black lead."At that time, shepherds in Barrodal often used graphite to mark sheep. Inspired by this, people cut graphite blocks into small strips to write and draw. Soon, King George II of England took the Barrodal graphite mine for the royal family, making it a royal patent product. Writing with graphite strips was not only dirtying hands, but also easy to break. In 1761, German chemist Faber first solved this problem. He washed graphite with water, turned graphite into graphite powder, then mixed it with sulfur, antimony, and rosin, and then made this mixture into strips. This was much more flexible than pure graphite strips and was not easy to dirty hands. This is the earliest pencil. Until the end of the 18th century, only England and Germany could produce this kind of pencil in the world. Therefore, after Napoleon launched wars against neighboring countries, England and Germany cut off the supply of pencils to France, so Napoleon ordered French chemist Condé to find graphite mines on his own land and then make pencils. However, the quality of French graphite mines was poor and the reserves were limited. Condé then added clay to graphite, put it in a kiln to bake, and made the pencil core that was both good and durable at that time in the world. The proportion of clay added to graphite is different, and the hardness of the pencil core produced is also different, and the color depth is also different. This is the origin of the markings H (hard pencil), B (soft pencil), and HB (pencil with moderate hardness and softness) that we see on today's pencils.
The task of covering the pencil with a wooden sleeve was completed by American craftsman Monroe. He first invented a machine that could cut wood strips, then carved fine grooves on the wood strips, inserted the pencil lead into the grooves, aligned and glued the two wood strips, and the lead was firmly embedded in the middle, which is the pencil we use today.