Use these 2-in-1 Flash Cards alone or add the Hot Dots Power Pen (sold separately) for exciting independent learning. Touch a correct answer and the Hot Dots Power Pen responds with lights and fun sounds. A gentle "Boing" sound with no light accompanies an incorrect answer. Cards explore time on the hour, half-hour, quarter-hour, and in 5- and 1-minute intervals. Includes 50 two-sided black and white flashcards in a convenient plastic case. Each card measures 3 1/2 x 5. Shipping weight: 8.3 oz.