This is a Matrixed Marble Machines pack that includes instructions and models to make a device that can operate like a starting gate. The first marble to enter is captured. The second marble to enter releases them both together and the race is off! Both marbles release together and travel down independent tracks. Additional materials required to build this model include neodymium magnets, and one 3/8" steel ball. Consult included documentation for an exact bill of materials.