Write ,Delete ,Repeat, Without Damaging Documents.No Wear Or Tear !Revolutionary Metamocolor Ink Technology - Thermo-Sensitive Gel Ink Disappears With Friction Using Rubber Tail Plug On The Pen,With No Debris (Ink Disappears At About 60C And Recovering Temperature Is Around -10C).Frixion Ball Can Write Repeatedly On The Same Spot With The Same Pen.Rubberized Grip To Ensure Comfortable Writing.Ideal For Sudoku,Puzzles, Crosswords And Everyday Writing.Strickly Not Recomended For Signatures,Examination Papers,Cheques Or Official Documents Where Writing Needs To Be Of A Permanent Nature.