Didax: Sandpaper numerals offer an important tactile experience for the young child, or those with special needs in learning correct numeral formation. Each card is covered with fine sand to help students make the connection between the physical movement of forming the number and the actual number shape. Each durable card has directional arrows to ensure proper formation and measures 2¾" x 4-5/16" and 5½" x 4 5/16". Set of 21 cards, 0-20.