Pilot's FriXion Colors markers produce solid color, plus mistakes are okay because the ink is erasable! Just by rubbing your writing with the rubber tip on the cap, your marks disappear cleanly. Not only great for fixing mistakes, this feature also lets you create interesting effects by erasing and then re-drawing over erased areas. Take error-free notes, color-code your ever-changing calendar, or write cute letters to friends.FriXion ink is a thermosensitive ink that can be erased by rubbing. Interestingly, erased ink reappears at temperatures below 14 Degree F (-10 Degree C). A freezer is cold enough to make this happen. It is like magic ink for adults! Due to the thermosensitive nature of FriXion ink, we advise against using it for mailings, or leaving the written materials in hot cars or in environments that expose them to a lot of frixion.