Reversible Flash Card Set 5″X7″ 20/Pkg-Black – Numbers 1-20 Kids will have fun while learning with these reusable chalkboard coloring flash cards. Each card features instructions on how to write the number and a sweet treat to color and decorate. The back of each card is blank so that kids can freely express their creativity. Works with chalk, chalk markers, chalk crayons or bright dry erase crayons. This package contains 20 5×7 inch reusable number cards.