F.U.N.? stands for Fluency & Understanding Numbers. In Kindergarten and First Grade, the F.U.N.? Empty Number Line can be a great tool for students' addition and subtraction, counting, counting on, decomposing numbers, as well as many other concepts. Includes number line hardware, activity guide and 210 cards specific to the Common Core Standards for Grades K-1, and 30 blank write-on/wipe-off cards.