The Casio FX-991CW ClassWiz is the UKs best-selling Advanced Scientific Calculator. It is an upgraded version of the Casio FX-991EX, containing additional features, to include a high definition display and improved menu navigation. Approved for Key stages 3, 4 and 5, recommended for Advanced GCSE, A/AS level and Highers. Allowed in every UK exam where a calculator can be used. The large Natural Textbook Display shows mathematical expressions like roots and fractions as they appear in your textbooks which increases comprehension because results are easier to understand.