Brighten up measuring, math lessons and art projects with these 6" Mood Rulers! Just like a mood ring, these vivid rulers change color with heat! Touch them and watch as the color morphs before your eyes. Includes purple, gree, blue, orange and red. Great for the classroom, school supplies, backpacks and pencil cases, these 6" rulers will come in handy for all your measuring needs! Fun for goody bags, too! Wood.