This is Noodler's rollerball pen that uses any fountain pen ink. The tip is user-replaceable at US$ 0.50 (50 cents )a piece. However, the tip was very dry and after letting it sit for a few days, it wouldn't start. So I pulled out the tip, removed the felt and now it writes like an EXTRA-FINE nib fountain pen. I filled it with Noodler's Bulletproof Black ink and use it as an all-purpose pen.