As many paper lovers know, Japanese ruled paper have a variety of different line widths. A study conducted in Japan showed users experienced frustration when trying to erase a single line of text in notes. This eraser has different sized edges aimed at erasing a single line from your notes. It has five widths: a point, 3 mm, 4 mm, 5 mm and 6 mm edge arranged in a five-point prism. Each edge has the number imprinted throughout the core, so even as you erase the number will still appear.