Smart Poly® material has been designed for charts in the classroom and home. The charts are strong, durable, water proof, and do not need lamination. The write-on/wipe-off surface is designed for dry erase or water based markers and washable crayons. Smart Poly Chart measures 13" x 19" with a heavy duty, glossy surface, .45mm. Grommet hole for easy hanging. Three pieces, no assembly required. Turn each wheel to pick a number. Choose a math computation by circling plus, minus, multiply or divide. Write out the equation, visualize and plot it on the number line.