This is a dedicated refill for the Dong-A U-Knock pen, featuring 0.5mm blue gel ink. Packaged in a dozen (12 count), it is an economical way to replace ink for offices or schools using existing U-Knock pens. A Korean-made product that provides stable writing quality, it is perfect for reducing stationery maintenance costs through bulk purchasing. This is a refill-only product; the pen body must be purchased separately.