You dont have to throw it, just shake it, and it acts just like regular dice! It rolls out slowly and flashes the last combination or "winning number"! Microprocessor controlled circuit is fun to learn. Runs on one 3V Lithium button cell (not included). Get two to simulate a pair of real dice to get "snake eyes" or "box cars"! Measures 1.4" x 1.4" x 1.3". From Velleman.