Pilot FriXion Erasable Synergy Knock 0.5mm 8-color set

The Pilot FriXion Synergy Knock gel pen writes smoothly and erases easily thanks to the FriXion's thermosensitive ink that uses the heat created when the built-in friction "eraser" is rubbed against paper to erase the ink. Make sure you don't write a bunch of important notes and then leave them in a hot car, because that too will cause the ink to disappear! Fear not, you can bring your notes back by putting them in the freezer. That's the magic of these pens!