The Casio FX-991MS is a handheld scientific calculator perfect for office and business use. With a regular key size and display size, this calculator is easy to use and provides accurate calculations. It is powered by both solar and battery sources, ensuring availability of power when needed. This calculator is manufactured by Casio, a trusted brand in the office equipment industry. The model FX-991MS is a reliable and efficient choice for those in need of a scientific calculator. Whether you're in a classroom, office, or business setting, this calculator is sure to meet your calculation needs.