Single refill for the Pilot Frixion Synergy Knock. This refill has the Synergy Tip, the hybrid needle-nose conical tip that ensures smooth writing with the finest of tip sizes. Available in your choice of pink, orange, green, light blue, and blue black and .3mm to .5mm tip sizes. If you’re looking for standard color options blue, black, or red, check out the refill 3-packs that are available. These refills are also compatible with pens such as the Frixion Synergy Knock Biz Marble and Frixion Point Knock.