Pilot 31572 FriXion Ball Erasable Pen, Purple Gel Ink, 0.7mm Fine Point. FriXion Ball Erasable Gel Pens allows you to erase and rewrite repeatedly without damaging documents. Thermosensitive, gel ink formula disappears with erasing friction of rubber plug eraser on the pen. Erasing leaves no residue or debris. Pen can write on the same spot that has been erased. Gel/rollerball pen delivers smooth writing gel ink and is not recommended for signatures, examination papers or official documents where writing needs to remain permanent or for exposure to extreme temperatures. Gel pen also earned the prestigious Good Housekeeping Seal.