Our felt-tip pens 9 + 1 colours, have a specially designed tip which cannot slip inside the pen or bend under pressure.  Featuring water-based inks, the felt -tip pens can be recharged by applying 2 drops of lemon juice or vinegar to the colour pad, which can be accessed by opening the back cap.  The pens have bright colours and can be used on many surfaces including paper, cardboard and wood etc.  Use the eraser-marker to remove the ink of the felt-tip pens from paper or many other surfaces.  The eraser-marker can be used as a secret ink, which only becomes visible after being drawn over with the felt-tip pens, providing children with lots of fun and creativity while drawing.