These marbles are ready to tumble down a run designed by you! Using the set's cling-back pieces, kids build tracks on walls and windows to solve the included STEM challenges! As they build, test, and tweak their marble runs, kids will also strengthen essential STEM skills, including critical thinking, problem solving and engineering. Includes 13 track pieces, 2 balls, and 10 double-sided STEM challenge cards. Grades K and up.