The fun, creativity and marvel of Marble Runs have been a favorite for boys and girls year in and year out. Unit blocks are the #1 must-have toy for preschoolers! Guidecraft has combined these two classics to create an instant classroom and home favorite. Our Unit Block Marble Run has been created using traditional unit blocks. It provides for the combination of the fun and lessons of marble runs with the traditions and educational foundations of unit block play. This set can be expanded easily by integrating it with traditional classroom unit blocks. Ages 3+.