F.U.N.™ stands for Fluency & Understanding Numbers. The F.U.N.™ Empty Number Line explores the extensive versatility of the number line, while incorporating a motivational manipulative aspect. It represents the number system while, at the same time, is a manipulative where numbers can be moved, matched and plotted, up and down the entire number line. The possibilities for using the number line to identify equivalent numbers are endless, including whole numbers, fractions, decimals, and negative numbers. Grade level cards sets are sold separately.