The Frixion Point Knock features Pilots unique Synergy tip, which combines the precision of a needle point with the durability of a conical point. These pens pair the same beloved thermosensitive ink found in other Frixion pens with a sleek, retractable pen body with metal mouthpiece and clip. Just push the clip to extend and retract the tip. The special rubber eraser at the top of each pen allows you to erase conveniently without pressing the retraction mechanism. Erase and rewrite repeatedly. Refillable with LFPKRF12S4.