The Sewline DUO MEDIUM POINT marker gives clean, clear lines with an even flow onto the fabric and without bleeding or penetrating into the fabric layers. The DUO Eraser contains a non toxic 'antidote' so when you guide the chisel point over the marks they simply evaporate away. This Sewline ink is breakthrough technology. Tested to ensure that once erased, marks will not reappear. Importantly, when marks are under stitching and have been for many months, they will still cleanly erase.