If you're going to follow the class with a ballpoint pen other than SIGNO UNIVOL 0.28, please avoid the knock-on ballpoint pen! The ballpoint pen to be used in class is a neutral pen, and the knock-type ballpoint pen is a yuseong pen, which is different from the other type of ink. 😵 Typical types of yuseong pen are Monami pen and BIG pen. The recommended ballpoint pen for class preparation is Signo Univol 0.28. If it's hard to get this ballpoint pen, I recommend high-tech 0.3!