LEONIS Water Erasable Pen & Air Erasable Pen Set [ 91620 ] Blue--Not spontaneously disappear,erasable by only water. Red--It will disappear within 2-10 days from most fabrics.(But can be immediately erased with water) Ideal for needlework and craft projects of all kinds Smaller than a normal pen to store in a small space Fine point, makes it easier to write small letters