The Pilot Frixion Ball Knock 4 Colour Gel Ink Multi Pen combines three erasable FriXion gel inks in one solid pen body. It includes 4 colours, black, blue, red and green Frixion gel inks. The special pilot ink technique - when the temperature reaches the point, the ink becomes transparent automatically by rubbing with the rubber at the end of the pen. The change of the ink is based on the change of temperature and won't leave any dirt. The pen has a rubber grip for writing comfort. Its spring-loaded clip allows you to secure it easily to your pocket or notebooks. The large size rubber “eraser” tip at the end allows you to erase conveniently.