The invention provides a pen. The pen comprises a pen body, an ink container prepared from a hard material is fixedly installed in the pen body, the bottom surface of the ink container is fixedly connected with the upper end of an ink
pipe, and the ink
pipe is communicated with the inside of the ink container. A
piston is arranged in the ink container, the
piston is collinear with the central lineof the ink container, the periphery of the
piston makes cooperative contact with the inner wall of the ink container, and the piston can slide up and down along the ink container. An
insertion hole is formed in the top surface of the piston, the top surface of the
insertion hole is communicated with the outside,
insertion grooves are formed in the front face and the rear face of the insertion hole respectively, the top surfaces of the insertion grooves are communicated with the outside, and the insertion grooves are communicated with the inside of the insertion hole. Arc-shaped grooves are formed in the two sides of each insertion groove respectively, and the arc-shaped grooves are communicated with the insides of the corresponding insertion grooves. The pen further comprises an adjustingrod and a dust-proof plug, wherein the dust-proof plug can be inserted into a through hole in the top surface of the pen body, and the periphery of the dust-proof plug can make close cooperative contact with the inner wall of the through hole in the top surface of the pen body so that dust and other debris can be prevented from entering the pen body through the through hole.