This is one refill for the Pilot FriXion Ball Slim gel ink pen or Pilot FriXion Ball 3 3 Color gel ink multi pen. It is interchangeable with Pilot's FriXion multi pen refills (model number LFBTRF30EF).
Q: My Pilot FriXion pen is not writing well. It seems to be dried out or writing with clear ink. What should I do?
The FriXion ink formula is thermo-sensitive, which causes it to become invisible when heat from friction is applied. If the pen has been exposed to warm temperatures or direct sunlight, this may have caused the ink inside the pen to be "erased." Please try to store the pens in your freezer overnight, then remove them for an hour or two prior to writing to allow them to come back to room temperature. This can usually reactivate the coloring in the ink and allow the pens to write as normal.