【DUAL POWER】Solar (works only when it is bright) and Battery (one AA battery NOT included). Automatically Power off, save more energy. Note: Please insert one AA battery for continuous and accurate usage【12 DIGITS CALCULATOR】12 digits make the calculator most useful for large calculations. Suitable for businessman, worker, teacher, student or anybody that needs make any sort of calculation from time to time【BIG BUTTON DESIGN】Large non-stick plastic button, new material, more durable. The calculators adopt scientific big button design in line with the use of human habits and comfortable for touch【LARGE DISPLAY】Large eye-angled, upright display, easy to read, easy to carry【NEW FUNCTION KEYS】Square Root, Auto Replay and Check keys are added. More functions, more facility!