0.5mm black refill for

Ultra-low-viscosity is ink that is "smooth" and easy-flowing like salad oil. When using "smooth" ink, an ordinary pen tip will have ink leakage, so it must be combined with an ultra-precisely processed pen tip. Anterique ballpoint pens use a pen tip with a built-in spring to precisely control the flow of ink for a very crisp, non-smudging, ultra-fine .5mm line.  This is the secret to smooth writing!  Made in Japan.