In fact, the difference between the needle type refill and the bullet type is the thickness of the refill. Because the bullet type is self-contained, it can be used with very thick refills. The thickest can be above 1.2. This is neutral. The pen is very thick. Most of what we need in our daily life is the needle tube type because it is generally in the range of 0.3-0.5. Here it involves the difference between a half needle tube and a full needle tube. It is the difference in thickness. It can be considered that the refill of the semicircular tube is a little thinner, basically the specification of 0.3, and the maximum that the full needle tube can reach is 0.4 or more. The difference between the two can be convenient on different occasions. We choose a refill that is more suitable for our own use.
