The Pilot Frixion Ball Knock Size 0.7 Erasable Pens come in a wide variety of colors - 10 colors to be exact! As a 0.7 size, strokes are nice and thick. Ink appears to erase cleanly from the page due to the heat produced from the friction of the rubbing of the eraser. Ink is thermo responsive/sensitive and it is highly recommended not to leave anything written in this ink in a heated environment (i.e. hot car). Also not recommended to be used on papers that may come into contact with heat during processing such as (but not limited to) mailings, cheques, etc. Erased ink can also reappear in -10C degrees.