Our exciting color-coded learning system offers so many benefits you'll never want to use an other type of flash card again. Our classroom tests prove that: Color-coding enhances self-esteem: Peer comparisons are not so easily made when one child is working on her " purple" facts and another is working on his " orange facts. Color-coding makes clean up easy: Students can sort and store by color, making the cards perfect for learning centers. Color-coding allows for individualized learning: Assigning students a color to master allows students to pull apart the flash card set and focus on a specific number family. Plus, color is appealing to kids. Order extra rings for sorting the 169 cards into smaller sets. Put each colored number family on its own ring for students to check out and take to their desks or home for practice, and still have lots of ringed sets available for other students to work on. Toss them in a box ... no problem. Finding the colored cards is easy. 6 rings per pack. 2" diameter.