Description The Retro 51 Tornado Pencil in Sudoku is a 1.15 mm pencil that operates with a simple twist of the top and has a huge eraser on top for those of us who make an occasional mistake. The Sudoku Pencil features a lacquer finish over stainless steel, with a sudoku puzzle printed on the barrel of the pen. The pencil comes with a generous supply of extra lead and erasers.