Opened container but unused, these Hongdian converters fit both the original manufacturer’s pens and the Zebra V-301 fountain pen commonly available in the US. Refill cartridges in black ink only are available for around $3.50 for a pack of two. This converter allows for fountain pen inks of any color to be used in the V-301. I’ve tested mine with black and blue. Breathe new life into your V-301 or Hongdian pen with this converter!